Showing papers in "Marine and Freshwater Research in 2014"
TL;DR: It is found that the reported long-term loss of natural wetlands averages between 54–57% but loss may have been as high as 87% since 1700 AD, and there has been a much faster rate of wetland loss during the 20th and early 21st centuries.
Abstract: It has been frequently stated, but without provision of supporting evidence, that the world has lost 50% of its wetlands (or 50% since 1900 AD). This review of 189 reports of change in wetland area finds that the reported long-term loss of natural wetlands averages between 54–57% but loss may have been as high as 87% since 1700 AD. There has been a much (3.7 times) faster rate of wetland loss during the 20th and early 21st centuries, with a loss of 64–71% of wetlands since 1900 AD. Losses have been larger and faster for inland than coastal natural wetlands. Although the rate of wetland loss in Europe has slowed, and in North America has remained low since the 1980s, the rate has remained high in Asia, where large-scale and rapid conversion of coastal and inland natural wetlands is continuing. It is unclear whether the investment by national governments in the Ramsar Convention on Wetlands has influenced these rates of loss. There is a need to improve the knowledge of change in wetland areas worldwide, particularly for Africa, the Neotropics and Oceania, and to improve the consistency of data on change in wetland areas in published papers and reports.
1,209 citations
TL;DR: Effective E-flows need to be explicit about flow-ecology relationships to adequately determine the amount and timing of water required and suggest four initial steps that will improve the applicability, implementation and ultimate success of E-flow methods.
Abstract: Providing flows for biota and environmental processes is a challenging water management issue. For society the ability and willingness to allocate water to sustain the environment is increasingly competitive due to escalating demand and as a consequence of climate change. In response, an array of environmental flow (E-flow) methods have developed. Our view is that few E-flows have been implemented and even fewer evaluated in a research and management context. Much of our science effort in E-flows has been directed primarily at method development, with less attention being given to monitoring, evaluation and subsequent revision of E-flow strategies. Our objectives are to highlight the lack of connection between current trends in E-flow literature and theory with assessment of the efficacy and practical application of these methods. Specifically, effective E-flows need to be explicit about flow-ecology relationships to adequately determine the amount and timing of water required. We briefly outline the historical development of E-flows and discuss how serial development of methods and techniques has restricted implementation, evaluation and revision. We highlight areas where methods are lacking, such as incorporation of data on flow-ecology relationships into operational use of E-flow methods. We suggest four initial steps that will improve the applicability, implementation and ultimate success of E-flows.
149 citations
TL;DR: Only one of the Microcystis strains (AB2011/53) produced microcystins (35 variants), indicating that mcyE is not a good surrogate for microcyStin production in environmental samples, and in eight non-microcystin-producing MicrocyStis strains, indicating that the diversity of cyanobacterial species and toxins is most probably underestimated.
Abstract: The South African Hartbeespoort Dam is known for the occurrence of heavy Microcystis blooms. Although a few other cyanobacterial genera have been described, no detailed study on those cyanobacteria and their potential toxin production has been conducted. The diversity of cyanobacterial species and toxins is most probably underestimated. To ascertain the cyanobacterial composition and presence of cyanobacterial toxins in Hartbeespoort Dam, water samples werecollectedinApril2011.Inapolyphasicapproach,27isolatedcyanobacterialstrainswereclassifiedmorphologically and phylogenetically and tested for microcystins (MCs), cylindrospermopsin (CYN), saxitoxins (STXs) and anatoxin-a (ATX) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and screened for toxin-encoding gene fragments. The isolated strains were identified as Sphaerospermopsis reniformis, Sphaerospermopsis aphanizomenoides, Cylindrospermopsis curvispora, Raphidiopsis curvata, Raphidiopsis mediterrranea and Microcystis aeruginosa. Only one of the Microcystis strains (AB2011/53) produced microcystins (35 variants). Forty-one microcystin variants were detected in the environmental sample from Hartbeespoort Dam, suggesting the existence of other microcystin producing strains in Hartbeespoort Dam. All investigated strains tested negative for CYN, STXs and ATX and their encoding genes. ThemcyEgeneofthemicrocystingeneclusterwasfoundinthemicrocystin-producingMicrocystisstrainAB2011/53and in eight non-microcystin-producing Microcystis strains, indicating that mcyE is not a good surrogate for microcystin production in environmental samples. Additional keywords: Cylindrospermopsis, Hartbeespoort Dam, microcystin, Microcystis, Raphidiopsis, Sphaerospermopsis.
63 citations
TL;DR: The paper outlines and justifies the techniques being implemented and the role the GMW might play in supporting national and international policy development, implementation and evaluation to the long-term conservation of mangrove ecosystems and the services they provide to society.
Abstract: Information on the status of and changes in mangroves is required for national and international policy development, implementation and evaluation. To support these requirements, a component of the Japan Aerospace Exploration Agency's (JAXA) Kyoto and Carbon (KC (2) to quantify changes in the structure and associated losses and gains of carbon on the basis of canopy height and above- ground biomass (AGB) estimated from the shuttle radar topographic mission (SRTM; acquired 2000), the ice, cloud and land-elevation satellite (ICESAT) geoscience laser altimeter system (GLAS; 2003-2010) and L-band backscatter data; (3) to determine likely losses and gains of tree species diversity through reference to International Union for the ConservationofNature(IUCN)globalthematiclayersonthedistributionofmangrovespecies;and(4)tovalidatemapsof changesintheextentofmangroves,primarilythroughcomparisonwithdensetime-seriesofLandsatsensordataandtouse these same data to describe the causes and consequences of change. The paper outlines and justifies the techniques being implementedandtherolethattheGMWmightplayinsupportingnationalandinternationalpoliciesthatrelatespecifically to the long-term conservation of mangrove ecosystems and the services they provide to society.
52 citations
TL;DR: Species with high constitutive expression of HSP and/or high degree of euryhalinity (cichlids) could potentially use estuaries as bridges, especially through areas of salinity ,15.
Abstract: Non-native freshwater fishes may spread via estuaries, invading nearby basins. The Brazilian natives Rhamdia quelen and Geophagus brasiliensis, and the worldwide introduced Clarias gariepinus, Ictalurus punctatus, Oreochromis niloticus and Cyprinus carpio were acutely exposed (6h) to salinities 15 and 30. Hypothetically, the introduced species display greater physiological plasticity than do the natives. Exposure to salinity 30 was lethal after 1.5-3h to all species except for O. niloticus and G. brasiliensis. Increase in plasma osmolality was inversely related to muscle water content, mainly in salinity 30 for all species. R. quelen and C. gariepinus displayed increased expression of heat-shock protein 70 (HSP70) on salinity increase; differently, I. punctatus, O. niloticus and C. carpio showed high constitutive levels already in freshwater. Species with high constitutive expression of HSP and/or high degree of euryhalinity (cichlids) could potentially use estuaries as bridges, especially through areas of salinity ,15. Additionalkeywords: biologicalinvasions,environmentalmatching,heat-shockprotein,musclewater,osmoregulation, physiological tolerance.
39 citations
TL;DR: Results from the WNA validated vertebral age estimates up to 12 years, but indicated that ages of large adult sharks were underestimated by 11–12 years, and age was also underestimated for adult sharks from the SIO by 14–18 years.
Abstract: Bomb radiocarbon analysis of vertebral growth bands was used to validate lifespan for sand tiger sharks (Carcharias taurus) from the western North Atlantic (WNA) and southwestern Indian Oceans (SIO). Visual counts of vertebral growth bands were used to assign age and estimate year of formation (YOF) for sampled growth bands in eight sharks from the WNA and two sharks from the SIO. Carbon-14 results were plotted relative to YOF for comparison with regional Δ14C reference chronologies to assess the accuracy of age estimates. Results from the WNA validated vertebral age estimates up to 12 years, but indicated that ages of large adult sharks were underestimated by 11–12 years. Age was also underestimated for adult sharks from the SIO by 14–18 years. Validated lifespan for C. taurus individuals in the present study reached at least 40 years for females and 34 years for males. Findings indicated that the current age-reading methodology is not suitable for estimating the age of C. taurus beyond ~12 years. Future work should investigate whether vertebrae of C. taurus record age throughout ontogeny, or cease to be a reliable indicator at some point in time.
39 citations
TL;DR: In this paper, in situ photosynthetic efficiency (FV/FM), dissolved and particulate nutrients, iron biological uptake, and nitrogen and carbon fixation were used to determine the factor-limiting phytoplankton growth and productivity in the North Tasman Sea and the subantarctic zone (SAZ).
Abstract: The Tasman Sea and the adjacent subantarctic zone (SAZ) are economically important regions, where the parameters controlling the phytoplankton community composition and carbon fixation are not yet fully resolved. Contrasting nutrient distributions, as well as phytoplankton biomass, biodiversity and productivity were observed between the North Tasman Sea and the SAZ. In situ photosynthetic efficiency (FV/FM), dissolved and particulate nutrients, iron biological uptake, and nitrogen and carbon fixation were used to determine the factor-limiting phytoplankton growth and productivity in the North Tasman Sea and the SAZ. Highly productive cyanobacteria dominated the North Tasman Sea. High atmospheric nitrogen fixation and low nitrate dissolved concentrations indicated that non-diazotroph phytoplankton are nitrogen limited. Deck-board incubations also suggested that, at depth, iron could limit eukaryotes, but not cyanobacteria in that region. In the SAZ, the phytoplankton community was dominated by a bloom of haptophytes. The low productivity in the SAZ was mainly explained by light limitation, but nitrogen, silicic acid as well as iron were all depleted to the extent that they could become co-limiting. This study illustrates the challenge associated with identification of the limiting nutrient, as it varied between phytoplankton groups, depths and sites.
38 citations
TL;DR: characterised the proximate composition of 11 previously identified groups of their potential prey and showed that, in the most, zooplankton species provide a reliable source of protein, suggesting that a narrow range of zoopLanktonspecies high in lipid are likely to be targeted by late-stage phyllosomas.
Abstract: Despite the global significance of spiny lobsters, the biology of their planktonic larvae, especially their carnivorous diet, is very poorly understood. Unsuitable diets and feeding regimes are one of the major reasons for consistently high mortalities during larval culture. In an effort to begin to determine the nutritional requirements of phyllosoma larvae of the spiny lobster, Jasus edwardsii, the present study first characterised the proximate composition of 11 previously identified groups of their potential prey. This included gelatinous zooplankton (chaetognaths, ctenophores, tunicates, siphonophores, scyphozoans, heteropods and pteropods), crustacean zooplankton (amphipods, copepods and euphausiids) and fish larvae. The composition of the 54 samples of 30 species of zooplankton ranged over 79.2–98.1% moisture content, and 1.9–54.2% for protein, 0.4–11.2% for carbohydrate, 0.1–27.9% for lipid, and 3.9–76.4% for ash of dry weight. The results showed that, in the most, zooplankton species provide a reliable source of protein. Only a small number of zooplankton had high lipid yield, suggesting that a narrow range of zooplankton species high in lipid are likely to be targeted by late-stage phyllosomas. The results of the present study will be useful as a guide for the development of artificial diets to improve phyllosoma aquaculture.
37 citations
TL;DR: In this article, the authors used the Gibbs diagram as a model for evaluating changes to ionic composition linked to urban development in 21 waterways in the Georges River catchment, Sydney.
Abstract: The geochemical signature of freshwater streams can be used to determine the extent and nature of modification to stream water geochemistry due to urban development. This approach used the Gibbs (1970) diagram as a model for evaluation of changes to ionic composition linked to urban development. In this multi-year study, the geochemistry of 21 waterways in the Georges River catchment, Sydney, were monitored and compared with the level of urban development as measured by sub-catchment imperviousness and directly connected imperviousness. The results reflect a strong relationship between the intensity of sub-catchment urban development and stream geochemistry. All major geochemical attributes increased with escalating levels of urban development. The largest increase was for bicarbonate, which increased 18 times from a mean of 6.4 mg L–1 at non-urban streams to a mean of 118 mg L–1 at urban streams. Similarly, mean concentrations of calcium increased by 14 times (from 2 to 27.9 mg L–1). Mean salinity was enriched in the most urban streams, compared with non-urban streams, by more than 6 times. We attribute this, in part, to the influence of urban geology, notably concrete stormwater infrastructure. Changes in stream geochemistry due to urban development are an important element of the urban stream syndrome.
35 citations
TL;DR: In this article, a 2-year, large-scale field experiment in a terminal wetland of the lower River Murray (South Australia) evaluated the effects of free-ranging carp on water transparency, aquatic macrophytes (biomass and cover), zooplankton density, benthic invertebrates (density, richness and diversity) as well as native fish.
Abstract: Common carp, Cyprinus carpio, is a highly invasive fish species across freshwater systems of south-eastern Australia, and especially in semi-arid floodplain wetlands. However, multi-component, large-scale experimental studies on carp effects on such ecosystems are scarce. This is in spite of demands to prioritise management and control of carp for the rehabilitation of habitats across the Murray–Darling Basin. A 2-year, large-scale field experiment in a terminal wetland of the lower River Murray (South Australia) evaluated the effects of free-ranging carp on water transparency, aquatic macrophytes (biomass and cover), zooplankton density, benthic invertebrates (density, richness and diversity) as well as native fish. Within 1 year since artificial inundation, transparency sharply decreased and this was accompanied by a decrease in aquatic macrophyte biomass and cover, a fluctuation in zooplankton density, and a decrease in benthic invertebrate richness and diversity. Also, the decreases in transparency and benthic invertebrate richness were significantly related to carp biomass, which averaged 68.0 kg ha–1 and induced a shift from clear- to turbid-water state. Following a flood event, increased connectivity caused carp to further access the newly inundated areas.
34 citations
TL;DR: It is demonstrated that ecosystem services were consistently under-recognised and that the failure to recognise the benefits is greatest for the ecosystem services provided by wetlands and in particular for supporting services.
Abstract: Ecosystems, and wetlands in particular, provide services that support and enhance human well being. In an increasingly urbanising world, the appropriate planning and management of ecosystem services can benefit a growing urban population. In 2011 UN-Habitat’s Governing Council adopted a Resolution that provided a mandate to promote biodiversity, wetlands and ecosystem services within the human settlement agenda. Subsequently, and developed in collaboration with UN-Habitat, in 2012 the Ramsar Convention also adopted a Resolution on the principles for the planning and management of urban and periurban wetlands and invited countries to raise awareness of the importance of wetlands to urban populations. This paper considered case studies drawn from cities across the globe in order to understand the level of awareness of ecosystem services from urban areas. The study demonstrated that ecosystem services were consistently under-recognised and that the failure to recognise the benefits is greatest for the ecosystem services provided by wetlands and in particular for supporting services. To ensure that the obligations under the two resolutions are implemented, and that urbanisation delivers high levels of societal well being, will require the development, dissemination and adoption of practical tools and a more robust integration of ecosystem services into urban planning and decision-making.
TL;DR: This study estimated age and growth of the largest extant fish, the whale shark (Rhincodon typus) by counting vertebral band pairs from 92 specimens comprising 43 males and 30 females taken by Taiwanese commercial fisheries during 2001–06.
Abstract: This study estimated age and growth of the largest extant fish, the whale shark (Rhincodon typus) by counting vertebral band pairs from 92 specimens comprising 43 males (2.68–9.88 m total length [TL]), 30 females (1.60–7.02 m TL), and 19 unsexed individuals (2.83–6.67 m TL) taken by Taiwanese commercial fisheries during 2001–06. Growth band pairs up to 25 and 42 were counted for a 6.38-m TL female and a 9.88-m TL male, respectively. Using marginal increment ratio and centrum edge analysis, band pairs were postulated to be formed twice a year. The two-parameter von Bertalanffy growth function provided the best fit without significant differences between sexes. Growth parameters were calculated for both sexes as L∞ = 16.80 m TL, k = 0.037 year–1; annual band pair formation would modify these parameters to L∞ = 15.34 m TL, k = 0.021 year–1. Using data reported in another study for 50% size at maturity for males (8.1 m TL), and the largest immature and smallest mature females (8.7 and 9.6 m TL, respectively) in the Indo-Pacific, these TLs converted to ages at maturity of 17 years for males and 19–22 years for females. The longevity was calculated to be 80.4 years.
TL;DR: Culvert designs can be improved by limiting water velocities to accommodate weak-swimming fishes and by accounting for the thermal sensitivity of swimming performance, as well as providing estimates of maximum water velocity allowing upstream fish passage.
Abstract: Fish passage through road culverts is poorly understood, particularly for small-bodied fishes, despite this information being integral to the restoration of waterway connectivity. We assessed the prolonged swimming performance of a small-bodied fish, empire gudgeon (Hypseleotris compressa; 3.2-7.7cm total length, TL), and juvenile Australian bass (Percalates novemaculeata; 3.5-7.8cm TL). Swimming trials were conducted in a hydraulic flume across a range of fixed and increasing velocities in response to acute and long-term thermal treatments. A new statistical approach (Tobit analysis) was used to relate the thermal dependence of swimming endurance to hydraulic characteristics of culverts, providing estimates of maximum water velocity allowing upstream fish passage. Reductions in water temperature of 10°C, similar to those caused by cold-water releases from dams, significantly impaired critical swimming speeds of both species. Traversable water-velocity models identified H. compressa as a weak swimmer, requiring very low water velocities (≤0.10ms-1 or 2.86 body lengths (BL) s-1) for unrestricted passage, whereas P. novemaculeata was predicted to traverse water velocities of ≤0.39ms-1 or 12.12BLs-1. Culvert designs can be improved by limiting water velocities to accommodate weak-swimming fishes and by accounting for the thermal sensitivity of swimming performance.
TL;DR: In this article, the relationship between flooding and lateral recharge and condition of the dominant riparian tree species, Eucalyptus camaldulensis, was determined between 2007 and 2011 using the Landsat (LTM5) Normalised Difference Vegetation Index (NDVI).
Abstract: Riparian forest and woodlands of the lower River Murray floodplain are exhibiting deteriorating health as a result of anthropogenic alterations to flow regimes and south-eastern Australia’s long-term ‘Millennium Drought’ from 1997 to 2009. Extensive flooding in 2010/2011 brought the drought to an end, providing an opportunity to monitor ecological floodplain recovery. The relationship between flooding and lateral recharge and condition of the dominant riparian tree species, Eucalyptus camaldulensis, was determined between 2007 and 2011 using the Landsat (LTM5) Normalised Difference Vegetation Index (NDVI). Linking the river hydrograph with the River Murray Floodplain Inundation Model (RiM-FIM) allowed exploration of the relationship between inundation duration and E. camaldulensis water requirements. Results indicate lateral bank recharge is an important mechanism in the maintenance of vegetation condition along the River Murray channel. Higher in-channel irrigation water delivery during summer months was identified as critical to survival of trees adjacent to the channel during the drought. The research suggests that weir pool manipulation to create in-channel flood pulses will aid E. camaldulensis maintenance. Furthermore, release of environmental flows once every 3 to 5 years to create bank-full flow or preferably overbank flows, will increase hydrological connectivity between river banks, wetlands and riparian zones, providing positive ecological benefits to E. camaldulensis and other floodplain and aquatic ecological assets.
TL;DR: A synergistic bio-control program using CHV-3, followed by a gene technology-based sex-ratio distortion program, is potentially the most effective strategy for reducing carp biomass by over 90% in the long term.
Abstract: To evaluate strategies within a carp-control plan, we developed a meta-population model of the geographic arrangement, biological connections and ‘unfished’ stock structure of the pest population of common carp (Cyprinus carpio) in a large river catchment. The model was tuned to recent observations of biomass. Published data were used to estimate sampling biases and yield from available carp-control tools. We simulated proposed carp-removal activities and also the potential effects of biological-control options; cyprinid herpesvirus-3 (CHV-3) and daughterless-carp gene technology. Outputs compared the population abundance before carp control (before 2009) and after a ~70-year period of sustained management. Models suggest that the proposed levels of carp removal may reduce biomass by ~50%. Although substantial, this control level may not be sufficient to reduce carp biomass densities below thresholds associated with ecological damage. In contrast, a CHV-3 bio-control program has potential to reduce carp biomass densities to, or exceeding, target levels, if mortality rates exceed 30% and broad-scale outbreaks occur in at least 40% of years, despite the likely development of resistance. A synergistic bio-control program using CHV-3, followed by a gene technology-based sex-ratio distortion program, is potentially the most effective strategy for reducing carp biomass by over 90% in the long term.
TL;DR: The present study has provided important baseline information, enabling comparison of the acute sensitivity of A. pulchella to trace metals with other marine invertebrates, and guiding the development of sublethal endpoints.
Abstract: The zooxanthellate sea anemone Aiptasia pulchella is found throughout the tropical and subtropical oceans of the Indo-Pacific and is easily maintained in aquaria, posing potential suitability as a standard tropical marine test organism for use in ecotoxicology. To gain an understanding of the sensitivity of A. pulchella to trace metals, 96-h static-renewal toxicity tests were conducted. Values of 96-h LC50 between 946 and 1196 µg L–1 were estimated for cadmium, between 595 and 1146 µg L–1 for zinc, 8060 and 12 352 µg L–1 for lead and 2209 and 5751 µg L–1 for nickel. In addition, preliminary assessment of rapid tentacle retraction was made. Six-hour EC50 values of 355 and 979 µg L–1 for cadmium, between 384 and 493 µg L–1 for zinc, between 2340 and 2584 µg L–1 for nickel, and 2610 µg L–1 for lead, were estimated for ‘severe’ tentacle retraction. Cobalt concentrations up to 1547 µg L–1 caused extreme zooxanthellae loss, but no more than 10% mortality and no rapid ‘severe’ tentacle retraction. The present study has provided important baseline information, enabling comparison of the acute sensitivity of A. pulchella to trace metals with other marine invertebrates, and guiding the development of sublethal endpoints.
TL;DR: Egg counts confirmed that spawning events coincided with adult aggregations, whereas egg abundances peaked at night during the first 2 h of the run-out tide, and it is postulate that spawning and recruitment success of P. colonorum is attributable to its selective spawning habitats.
Abstract: Determining the links among estuarine hydrography, habitat and spawning of estuarine-dependent fish is essential for understanding reproductive dynamics, recruitment processes and directing conservation efforts. Acoustic tracking was used to evaluate fine-scale spatial and temporal patterns in spawning activity of Percalates colonorum (estuary perch) within the Shoalhaven River, south-eastern Australia. Plankton tows were used to determine the timing of spawning events. Tagged P. colonorum exhibited movements restricted to areas of structurally complex large wooden debris and a concrete ferry landing. Egg counts confirmed that spawning events coincided with adult aggregations, whereas egg abundances peaked at night during the first 2 h of the run-out tide. We postulate that spawning and recruitment success of P. colonorum is attributable to its selective spawning habitats that are (1) structurally complex to provide refuge and protection from predation, as well as congregate prey items, (2) adjacent to deep water of high velocities to maximise egg dispersal and (3) in close proximity to river entrance to facilitate coastal dispersal of eggs and inter-estuarine connectivity of larvae.
TL;DR: In this article, the authors used a set of 32 temporary ponds in northern Morocco to study the respective importance of local (within the pond) and regional (density of ponds in landscape) factors and the impacts of different land uses on the plant species assemblages.
Abstract: Identifying the respective role of environmental, landscape and management factors in explaining the patterns in community composition is an important goal in ecology. Using a set of 32 temporary ponds in northern Morocco we studied the respective importance of local (within the pond) and regional (density of ponds in landscape) factors and the impacts of different land uses on the plant species assemblages, separating pond and terrestrial species. The main hypotheses tested were that (1) species assemblages respond to both local and regional environmental factors, (2) anthropogenic pressure has a negative influence on the number of pond species, and that (3) human activities differ in their impact on pond biodiversity. The results showed that (1) local factors explain most of the variation in plant community composition, and (2) land use impacts the communities through changing local environmental conditions, leading to a loss of typical pond species. Aside from recreation, all other activities (grazing, drainage, agriculture and partial urbanisation) significantly reduced the number of pond species. The conservation strategy for rare pond species should focus on maintaining networks of oligotrophic ponds, while allowing only low-impact activities.
TL;DR: Declines in seagrass availability may reduce R. taylori presence in nearshore areas and may be relevant to spatial management of this species.
Abstract: Shark resource-use strategies affect how they will respond to changes within their environment and, as such, may be important to consider in conservation and management. Movement data on sharks that use nearshore areas is particularly valuable because these habitats are highly dynamic. The present study used passive acoustic telemetry to examine the space-use, habitat-selection and habitat-specialisation patterns of the Australian sharpnose shark, Rhizoprionodon taylori, in a nearshore area. Habitat selectivity and specialisation were assessed across five benthic habitat types, including outer bay, seagrass, reef, sandy inshore and intertidal mudflats. The majority of R. taylori sharks were present for short periods of time, ranging from 1 to 112 days (mean ± s.e. = 16.9 ± 4.9). Activity-space analysis indicated that R. taylori roamed widely, but monthly activity-space size was consistent among individuals and through time. Both the population and individuals displayed wide habitat niches, indicating that the species may be resilient to environmental change. However, R. taylori consistently selected for seagrass over other habitats, potentially for feeding. Therefore, declines in seagrass availability may reduce R. taylori presence in nearshore areas and may be relevant to spatial management of this species.
TL;DR: A lengthy and variable duration of the pre-settlement phase, along with a relatively consistent size-at-competence within closely related species, are suggested as mechanisms through which these fishes may increase their probability to settle in the spatially restricted habitat of exposed rocky pools.
Abstract: The planktonic duration (PD) was determined in fourteen intertidal rocky fishes from the south-eastern Pacific Ocean by counting the otolith micro-increments from hatch check to a transition mark (TM). TMs were validated by comparing the PDs estimated from post-settlers with the total increment counts from otoliths of more recent (new) settlers. In 11 species (79%), the most common TM corresponded to a notable decrease in increment width after settlement. The PDs ranged from 45 days in the kyphosid Girella laevifrons to 135 days in the labrisomid Auchenionchus variolosus, and eight species (57%) had mean PDs of longer than three months. The mean observed size-at-settlement (SASM) values ranged from 17.5 ± 7.2 mm TL in Gobiesox marmoratus (Gobiesocidae) to 40 ± 5.5 mm TL in Calliclinus geniguttatus (Labrisomidae) and showed low variability within species of the same family. PDs were markedly longer in intertidal rocky fishes than in other littoral and reef fishes in tropical and temperate waters. A lengthy and variable duration of the pre-settlement phase, along with a relatively consistent size-at-competence within closely related species, are suggested as mechanisms through which these fishes may increase their probability to settle in the spatially restricted habitat of exposed rocky pools.
TL;DR: The combined approach of molecular, stable isotope and behavioural studies have provided insight into the trophic ecology of this difficult-to-access environment, providing a framework for more fine-scale analyses of the diet of different-sized species to examine speciation underground.
Abstract: The Yilgarn calcrete aquifers in Western Australia are an interesting system for investigating the process of speciation within subterranean habitats, because of the limited opportunities for dispersal between isolated calcretes The presence of different-sized diving beetles (Dytiscidae) in separate calcretes, including sympatric sister-species pairs, suggests that species may have evolved within calcretes by an adaptive shift as a result of ecological-niche differentiation We have studied the potential for trophic niche partitioning in a sister triplet of diving beetles, of distinctly different sizes, from a single aquifer Fragments of the mitochondrial COI gene, specific to known species of amphipods and copepods, were polymerase chain reaction-amplified from each of the three beetle species, indicating that there is an overlap in their prey items Significant differences were found in the detected diets of the three species, and results showed a propensity for prey preferences of amphipods by the large beetles and one species of copepod for the small beetles A terrestrial source of carbon to the calcrete was suggested by stable isotope analyses The combined approach of molecular, stable isotope and behavioural studies have provided insight into the trophic ecology of this difficult-to-access environment, providing a framework for more fine-scale analyses of the diet of different-sized species to examine speciation underground
TL;DR: The complete fishing ban appeared to be to only effective tool in restoring target fish stocks and maintaining a higher stability of the fish assemblage whereas partial fishing prohibition failed to meet this goal.
Abstract: Marine reserves have become an important tool advocated to protect diversity, habitat or to restore depleted fish stocks. However, the links between reserve effect and temporal variability of assemblages remains equivocal. The present study presents the results obtained in a long-term series of annual surveys in the Scandola Marine Reserve (Corsica, North-western Mediterranean). An underwater visual census was performed on Posidonia oceanica seagrass beds. Species richness and density of target fish were positively affected by fishing prohibition in the no-take zone. The whole assemblage density and density of non-target and prey fish, prevailing in the seagrass bed, were not or negatively affected by fishing prohibition. Concomitantly, temporal stability was positively related to fishing prohibition. This stabilisation of the fish assemblage in the no-take zone had not been observed over rocky reefs in previous studies. This outcome may be linked to wandering predators of rocky areas, preying upon seagrass fish assemblages. In addition, the complete fishing ban appeared to be to only effective tool in restoring target fish stocks and maintaining a higher stability of the fish assemblage whereas partial fishing prohibition failed to meet this goal.
TL;DR: This radio-tracking study compared adult daytime microhabitat use by three large Australian native freshwater fishes and introduced carp in the Murray River, south-eastern Australia to describe habitat patches used by all species and quantifies differences among species.
Abstract: The present radio-tracking study compared adult daytime microhabitat use by three large Australian native freshwater fishes (Murray cod, Maccullochella peelii, trout cod, M. macquariensis, golden perch, Maquaria ambigua) and introduced carp, Cyprinus carpio, in the Murray River, south-eastern Australia. The paper describes habitat patches used by all species and quantifies differences among species. All species were strongly associated with structural woody habitat (>68% cover), deeper (>2.4 m), slower water ( 70% cover, be >1.5 m high, located <15% of the river channel (width) closest to the bank, with surface water velocities of 0.3–0.6 m s–1.
TL;DR: The results suggested that selection for high growth rate in GFP can be undertaken successfully before full market size has been reached and genetic correlations for body traits between ages were generally high.
Abstract: The aim of the current study was to estimate heritabilities and correlations for body traits at different ages (Weeks 10 and 18 after stocking) in a giant freshwater prawn (Macrobrachium rosenbergii) population selected for fast growth rate in Vietnam. The dataset consisted of 4650 body records (2432 and 2218 records collected at Weeks 10 and 18, respectively) in the full pedigree comprising a total of 18 387 records. Variance and covariance components were estimated using restricted maximum likelihood fitting a multi-trait animal model. Estimates of heritability for body traits (bodyweight, body length, cephalothorax length, abdominal length, cephalothorax width and abdominal width) were moderate and ranged from 0.06 to 0.11 and from 0.11 to 0.22 at Weeks 10 and 18, respectively. Body-trait heritabilities estimated at Week 10 were not significantly lower than at Week 18. Genetic correlations between body traits within age and genetic correlations for body traits between ages were generally high. Our results suggested that selection for high growth rate in GFP can be undertaken successfully before full market size has been reached.
TL;DR: It is concluded that submergence time and water salinity will affect the performance of mangrove areas, such that areas experiencing prolonged submergence with flooding dominated by saline water might be most severely impacted.
Abstract: Flooding and salinity fluctuations are common in mangrove systems. Sometimes these events are long-lasting, persisting several months. With an increased frequency of heavy rainfalls and terrestrial run-off, subsequent floods have been associated with massive mangrove mortality and failure to regenerate in the region. Owing to climate change, these events are expected to be more common in the future. We investigated how three weeks of submergence in water of different salinities affected the photosynthetic rates in seedlings of three common mangroves: Bruguiera gymnorrhiza (L.) Lamk.; Avicennia marina (Forssk.) Vierh.; and Heritiera littoralis Dryand. We found that photosynthesis and survival rates declined with increasing salinity and submergence time for all species. Prolonged submergence caused a significant decline in photosynthetic rates (as electron transport rate – ETR) for B. gymnorrhiza (P = 0.021) and H. littoralis (P = 0.002), whereas significant effects of both salinity (P = 0.003) and submergence (P = 0.023) were observed between species. Maximum diurnal values of ETR declined in the order of A. marina > B. gymnorrhiza > H. littoralis. After submergence, survived seedlings were tended normally, watered twice a day with freshwater. Three seedlings of B. gymnorrhiza from freshwater and 33% seawater treatments and of A. marina from freshwater treatment displayed signs of recovery for the first 3–5 days, but after that they died. We conclude that submergence time and water salinity will affect the performance of mangrove areas, such that areas experiencing prolonged submergence with flooding dominated by saline water might be most severely impacted.
TL;DR: In this paper, the authors analyzed the structure of a coastal fish community in Galicia (northwestern Spain) by comparing the following three techniques: diver-based underwater visual census (UVC), remotely operated vehicle (ROV) and remote underwater video (RUV).
Abstract: Comparative works on sampling techniques allow selecting the best methods to study each target fish community. We analysed the structure of a coastal fish community in Galicia (north-western Spain) by comparing the following three techniques: diver-based underwater visual census (UVC), remotely operated vehicle (ROV) and remote underwater video (RUV). All techniques detected abundant and frequent taxa, but divers obtained more precise and complete inventories (80% of identified taxa) than did ROV (60%) and RUV (47%), were faster (only 1.4 days to achieve the estimated taxa list) than were ROV (2.0 days) and RUV (475.7 days), and were more reliable in estimating the abundances of highly mobile, less abundant, less frequent, cryptic and smaller fish. Conversely, RUV obtained the poorest estimates of abundances, and even though it obtained more replicates (136), there were more zeros (98%) than with divers (16 replicates, 64% zeros) and ROV (11 replicates, 75% zeros). Furthermore, the economic cost of the video system was triple the cost of the diving gear; consequently, we recommend using divers to study the coastal fish communities in the shallow waters of the North Atlantic Ocean. However, further research is necessary to explore the full capabilities of video techniques in long-term studies, in greater depths and in adverse weather conditions.
TL;DR: In this paper, the authors developed techniques to identify in-stream waterholes across large and inaccessible areas of the Flinders and Gilbert catchments using Landsat imagery and applied this technique to 400 scenes between 2003 and 2010 to identify key waterhole refugia that are likely to persist during all years.
Abstract: Many northern Australian rivers have limited or non-existent dry season flow and rivers tend to dry to a series of pools, or waterholes, which become particularly important refugial habitat for aquatic biota during the periods between streamflow events. The present study developed techniques to identify in-stream waterholes across large and inaccessible areas of the Flinders and Gilbert catchments using Landsat imagery. Application of this technique to 400 scenes between 2003 and 2010 facilitated the identification of key waterhole refugia that are likely to persist during all years. Relationships for predicting total waterhole area from streamflow characteristics were produced for four river reaches. Using these relationships and streamflow predictions based upon climate data scaled using 15 global climate models, the potential impacts of future climate on waterhole persistence was assessed. Reductions in waterhole area of more than 60% were modelled in some years under drier scenarios and this represents a large reduction in available habitat for areas that already have limited in-stream refugia. Conversely, under wetter future climates the total area of waterholes increased. The approach developed here has applicability in other catchments, both in Australia and globally, and for assessing the impacts of changed flow resulting from water resource development.
TL;DR: Near infrared (NIR) spectroscopy was investigated as a potential rapid method of estimating fish age from whole otoliths of Saddletail snapper, indicating that Saddletails age could be predicted within 1.5 increment counts, and may have potential for other fish species.
Abstract: Near infrared (NIR) spectroscopy was investigated as a potential rapid method of estimating fish age from whole otoliths of Saddletail snapper (Lutjanus malabaricus). Whole otoliths from 209 Saddletail snapper were extracted and the NIR spectral characteristics were acquired over a spectral range of 800–2780 nm. Partial least-squares models (PLS) were developed from the diffuse reflectance spectra and reference-validated age estimates (based on traditional sectioned otolith increments) to predict age for independent otolith samples. Predictive models developed for a specific season and geographical location performed poorly against a different season and geographical location. However, overall PLS regression statistics for predicting a combined population incorporating both geographic location and season variables were: coefficient of determination (R2) = 0.94, root mean square error of prediction (RMSEP) = 1.54 for age estimation, indicating that Saddletail age could be predicted within 1.5 increment counts. This level of accuracy suggests the method warrants further development for Saddletail snapper and may have potential for other fish species. A rapid method of fish age estimation could have the potential to reduce greatly both costs of time and materials in the assessment and management of commercial fisheries.
TL;DR: The study demonstrated the value of a surrogacy approach to the prediction of biodiversity patterns, particularly when the number of biological samples was limited, and identified potential physical surrogates for species richness and abundance, with sediment physical properties ranked as most important across the study region.
Abstract: A key requirement for informed marine-zone management is an understanding of the spatial patterns of marine biodiversity, often measured as species richness, total abundance or presence of key taxa. In the present study, we focussed on the diversity of benthic infauna and applied a predictive modelling approach to map biodiversity patterns for three study sites on the tropical Carnarvon shelf of Western Australia. A random forest decision tree model was used to generate spatial predictions of two measures of infaunal diversity, namely, species richness and total abundance. Results explained between 20% and 37% of the variance of each measure. The modelling process also identified potential physical surrogates for species richness and abundance, with sediment physical properties ranked as most important across the study region. Specifically, coarse-grained heterogeneous sediments were associated with higher infaunal species richness and total abundance. Seabed topographic properties were also important at the local scale. The study demonstrated the value of a surrogacy approach to the prediction of biodiversity patterns, particularly when the number of biological samples was limited. Such an approach may facilitate an understanding of ecosystem processes in the region and contribute to integrated marine management.
TL;DR: Wang et al. as discussed by the authors investigated plant community structure and groundwater attributes in Ejina Delta in north-western China to understand spatial variability of groundwater depth and composition and their impacts on vegetation succession Geostatistical methods and ordination analysis were performed to analyse the data.
Abstract: Plant-community structure and groundwater attributes were investigated in Ejina Delta in north-western China to understand spatial variability of groundwater depth and composition and their impacts on vegetation succession Geostatistical methods and ordination analysis were performed to analyse the data In addition, we tried to obtain vegetationsuccessionalseriesbyusinganapproachofspatialsequencesinsteadoftemporalsequencesThefindingsofthe present study were as follows: (1) the coefficient of variation for groundwater depth (GWD), salinity (SAL), total dissolved solids (TDS), electrical conductivity (EC), pH, Ca 2þ ,M g 2þ ,K þ ,N a þ ,S O4� , HCO3 ,N O3 ,C land Franged from 004 to 153; (2) GWD, Mg 2þ , TDS, EC, Ca 2þ , HCO3 ,N O3 and pH showed strong spatial autocorrelation, whereas K þ and SAL showed moderate spatial autocorrelation; (3) canonical correspondence analysis revealed that groundwater heterogeneity, especially GWD, followed by pH, SAL, TDS, EC and HCO3 , had an important impact on vegetation succession,andthusshowedaprevalenceofgroundwaterattributes-basednichedifferentiationamongplantcommunities; and (4) there were two vegetation successional processes (drought and salinisation) in the lower Heihe River Basin, and salinisation processes increased with drought processes Our results indicated that high spatial variability of groundwater attributes contributes to promoting maintenance of species and landscape diversity in the lower Heihe River Basin Additional keywords: canonical correspondence analysis (CCA), groundwater heterogeneity, semi-variogram