Showing papers in "Marine Ecology Progress Series in 2017"
TL;DR: The effects of season (breeding vs. nonbreeding periods), breeding stage, breeding status, age, sex and individual specialization on foraging and migration strategies, as well as the consequences for population dynamics and conservation are reviewed.
Abstract: Technological advances in recent years have seen an explosion of tracking and stable isotope studies of seabirds, often involving repeated measures from the same individuals This wealth of new information has allowed the examination of the extensive variation among and within individuals in foraging and migration strategies (movements, habitat use, feeding behaviour, trophic status, etc) in unprecedented detail Variation is underpinned by key life-history or state variables such as sex, age, breeding stage and residual differences among individuals (termed ‘individual specialization’) This variation has major implications for our understanding of seabird ecology, because it affects the use of resources, level of intra-specific competition and niche partitioning In addition, it determines the responses of individuals and populations to the environment and the susceptibility to major anthropogenic threats Here we review the effects of season (breeding vs nonbreeding periods), breeding stage, breeding status, age, sex and individual specialization on foraging and migration strategies, as well as the consequences for population dynamics and conservation
107 citations
TL;DR: It is hypothesized that reef sponges convert the dissolved organic matter released by benthic primary producers into particulate detritus that is transferred to sponge-associated detritivores via the sponge loop pathway, thereby acting as key players within reef food webs.
Abstract: The high biodiversity of coral reefs results in complex trophic webs where energy and nutrients are transferred between species through a multitude of pathways. Here, we hypothesize that reef sponges convert the dissolved organic matter released by benthic primary producers (e.g. corals) into particulate detritus that is transferred to sponge-associated detritivores via the sponge loop pathway. To test this hypothesis, we conducted stable isotope (C-13 and N-15) tracer experiments to investigate the uptake and transfer of coral-derived organic matter from the sponges Mycale fistulifera and Negombata magnifica to 2 types of detritivores commonly associated with sponges: ophiuroids (Ophiothrix savignyi and Ophiocoma scolopendrina) and polychaetes (Polydorella smurovi). Findings revealed that the organic matter naturally released by the corals was indeed readily assimilated by both sponges and rapidly released again as sponge detritus. This detritus was subsequently consumed by the detritivores, demonstrating transfer of coral-derived organic matter from sponges to their associated fauna and confirming all steps of the sponge loop. Thus, sponges provide a trophic link between corals and higher trophic levels, thereby acting as key players within reef food webs.
69 citations
TL;DR: It is found that white sharks are more broadly distributed, both horizontally and vertically, throughout the North Atlantic than previously understood, exhibiting an ontogenetic shift from near-coastal, shelf-oriented habitat to pelagic habitat with frequent excursions to mesopelagic depths.
Abstract: In the western North Atlantic, much of what is known about the movement ecology of the white shark Carcharodon carcharias is based on historical fisheries-dependent catch records, which portray a shelf-oriented species that moves north and south seasonally. In this study, we tagged 32 white sharks (16 females, 7 males, 9 unknown), ranging from 2.4 to 5.2 m total length, with satellitebased tags to investigate broad-scale movements in the North Atlantic. Based on 10427 days of tracking data, we found that white sharks are more broadly distributed, both horizontally and vertically, throughout the North Atlantic than previously understood, exhibiting an ontogenetic shift from near-coastal, shelf-oriented habitat to pelagic habitat with frequent excursions to mesopelagic depths. During the coastal phase, white sharks migrated seasonally from the northeast shelf in the summer to overwintering habitat off the southeastern US and the Gulf of Mexico, spending 95% of their time at <50 m depth. During the pelagic phase, subadult and adult white sharks exhibited wide-ranging movements during the fall, winter, and spring into the broader Atlantic over a 30° latitudinal range and as far east as the Azores. These sharks moved daily to depths of up to 1128 m, spending significant time at specific mesopelagic depth zones through a temperature range of 1.6 to 30.4°C. We believe these movements are associated with offshore foraging facilitated by the thermal physiology of the species. Our findings extend the known essential habitat for the white shark in the North Atlantic beyond existing protection, with implications for future conservation.
62 citations
62 citations
TL;DR: This work demonstrates that Template Model Builder (TMB), a new R package, is an accurate, efficient and flexible framework for modelling movement data and discusses how TMB’s potential reaches beyond marine movement studies.
Abstract: Tracking of marine animals has increased exponentially in the past decade, and the resulting data could lead to an in-depth understanding of the causes and consequences of movement in the ocean. However, most common marine tracking systems are associated with large measurement errors. Accounting for these errors requires the use of hierarchical models, which are often difficult to fit to data. Using 3 case studies, we demonstrate that Template Model Builder (TMB), a new R package, is an accurate, efficient and flexible framework for modelling movement data. First, to demonstrate that TMB is as accurate but 30 times faster than bsam, a popular R package used to apply state-space models to Argos data, we modelled polar bear Ursus maritimus Argos data and compared the locations estimated by the models to GPS locations of these same bears. Second, to demonstrate how TMB’s gain in efficiency and frequentist framework facilitate model comparison, we developed models with different error structures and compared them to find the most effective model for light-based geolocations of rhinoceros auklets Cerorhinca monocerata. Finally, to maximize efficiency through TMB’s use of the Laplace approximation of the marginal likelihood, we modelled behavioural changes with continuous rather than discrete states. This new model directly accounts for the irregular sampling intervals characteristic of Fastloc-GPS data of grey seals Halichoerus grypus. Using real and simulated data, we show that TMB is a fast and powerful tool for modelling marine movement data. We discuss how TMB’s potential reaches beyond marine movement studies.
61 citations
TL;DR: In this article, the authors conducted research cruise around the South Shetland Islands of the Antarctic Peninsula during winters with contrasting ice conditions to examine potential interactions with the krill fishery.
Abstract: Climate change will affect Antarctic krill Euphausia superba, krill-dependent predators, and fisheries in the Southern Ocean as areas typically covered by sea ice become ice-free in some winters. Research cruises conducted around the South Shetland Islands of the Antarctic Peninsula during winters with contrasting ice conditions provide the first acoustic estimates of krill biomass, habitat use, and association with top predators to examine potential interactions with the krill fishery. Krill abundance was very low in offshore waters during all winters. In Bransfield Strait, median krill abundance was an order of magnitude higher (8 krill m−2) compared to summer (0.25 krill m−2), and this pattern was ob served in all winters regardless of ice cover. Acoustic estimates of krill biomass were also an order of magnitude higher (~5 500 000 metric tons [t] in 2014) than a 15 yr summer average (520 000 t). Looking at krilldependent predators, during winter, crabeater seals Lobodon carcinophagus were concentrated in Bransfield Strait where ice provided habitat, while Antarctic fur seals Arctocephalus gazella were more broadly distributed. Krill overwinter in coastal basin environments independent of ice and primary production and in an area that is becoming more frequently icefree. While long-term projections of climate change have focused on changing krill habitat and productivity declines, more immediate impacts of ongoing climate change include increased risks of negative fishery−krill−predator interactions, alteration of upper trophic level community structure, and changes in the pelagic ecology of this system. Development of management strategies to mitigate the increased risk to krill populations and their dependent predators over management timescales will be necessary to minimize the impacts of long-term climate change.
59 citations
58 citations
TL;DR: This work used a systematic search of over 3000 peer-reviewed papers to review the marine invasion literature, identify overarching patterns, and help direct future research on 4 biological mechanisms: negative interactions, invader traits, and post-introduction evolution, as they relate to understanding marine invasion success.
Abstract: With expanding trade resulting in increased global transport of non-native species, a broader understanding of the mechanisms of marine invasions is becoming increasingly crucial. Yet our understanding of marine invasions lags behind that of terrestrial invasions, and this includes our understanding of fundamental biological mechanisms that influence marine invasion success. We used a systematic search of over 3000 peer-reviewed papers to review the marine invasion literature, identify overarching patterns, and help direct future research. We focus on 4 biological mechanisms: negative interactions (e.g. limiting similarity, biotic resistance, enemy release, novel weapons), positive interactions, invader traits, and post-introduction evolution, as they relate to understanding marine invasion success. A total of 470 studies (264 non-native species) were reviewed, resulting in the largest review of biological mechanisms of marine invasions to date. Negative interactions and invader traits received the majority of attention in the literature. Most negative interaction studies documented an increase in invasion success resulting from avoidance or release from competitors or consumer pressure. Consumer pressure, and predation in particular, compared to competition was more commonly documented as a mechanism that can limit invasion success. Despite limited evaluation, positive interactions and post-introduction evolution showed potential for enhancing invasion success. Invader trait studies highlighted the importance of life history and stress tolerance traits. Future studies that examine interactions at multiple scales and utilize multi-faceted approaches, molecular techniques, and predictive modeling will en hance our knowledge and ability to develop strategies to protect native ecosystems.
53 citations
TL;DR: In this paper, the authors present a comprehensive, coastal marine food web that includes 147 taxa cooccurring on shallow subtidal reefs along the highly productive and exploited Humboldt Current System of central Chile.
Abstract: Food webs as representations of who eats whom are at the core of community ecology. Incorporation of tools from network theory enables assessment of how complex systems respond to natural and human-induced stressors, revealing how harvesting may degrade the properties and resilience of food webs. We present a comprehensive, coastal marine food web that includes 147 taxa cooccurring on shallow subtidal reefs along the highly productive and exploited Humboldt Current System of central Chile. This food web has connectance of 0.06, link density of 1204 and mean chain length of 4.3. The fractions of intermediate (76%), omnivorous (49%) and cannibalistic (8%) nodes are slightly lower than those observed in other marine food webs. Of the 147 nodes, 34 are harvested. Links to harvested nodes represented 50 to 100% of all trophic links of non-harvested nodes, illustrating the great impact that fishery pressure can have on the food web. The food web was compartmentalized into 5 sub-webs with high representation of harvested taxa. This structure changes if the fishery node is removed. Similarity analyses identified groups of harvested species with non-harvested nodes, suggesting that these tropho-equivalents could be sentinel species for the community-wide impacts of coastal fisheries. We conclude that fishing effects can be transmitted throughout the food web, with no compartments completely unaffected by harvesting. It is urgent to establish monitoring programs for community-wide effects of fisheries and assess whether resilience of these highly productive subtidal food webs has al ready been compromised, thereby identifying essential nodes that require stronger fisheries regulation.
52 citations
TL;DR: Investigating the spatial ecology of the opportunistic yellow-legged gull Larus michahellis found that the combination of individual specialization and individual spatial segregation may reduce intra-specific competition, with these 2 important mechanisms driving the success of this winning species.
Abstract: Population expansions of successful species have gained importance as a major conservation and management concern. The success of these ‘winners’ is widely attributed to their high adaptability and behavioural plasticity, which allow them to efficiently use opportunities provided by human-modified habitats. However, most of these studies consider conspecifics as ecological equivalents, without considering the individual components within populations. This is critical for a better understanding of the main ecological mechanisms related to the success of winning species. Here, we investigated the spatial ecology of the opportunistic yellow-legged gull Larus michahellis, a clear example of a winning species in southern Europe, to examine its degree of individual specialization in habitat use. To test for such individual strategies, we applied specialization metrics to spatial data obtained from 18 yellow-legged gulls that were GPS-tracked simultaneously during the breeding season. The results revealed that population-level generalism in habitat use in the yellow-legged gull arises through varying levels of individual specialization, and individual spatial segregation within each habitat. Importantly, we found that the combination of individual specialization and individual spatial segregation may reduce intra-specific competition, with these 2 important mechanisms driving the success of this winning species.
52 citations
TL;DR: In this article, the authors used time series from the Sir Alister Hardy Foundation for Ocean Science Continuous Plankton Recorder to demonstrate that longterm observations reveal both the prevalence of nonlinear processes in species abundances and an improvement in out-of-sample predictability as the number of observations increase.
Abstract: Although it seems obvious that with more data, the predictive capacity of ecological models should improve, a way to demonstrate this fundamental result has not been so obvious. In particular, when the standard models themselves are inadequate (von Bertalanffy, extended Ricker etc.) no additional data will improve performance. By using time series from the Sir Alister Hardy Foundation for Ocean Science Continuous Plankton Recorder, we demonstrate that longterm observations reveal both the prevalence of nonlinear processes in species abundances and an improvement in out-of-sample predictability as the number of observations increase. The empirical results presented here quantitatively demonstrate the importance of long-term temporal data collection programs for improving ecosystem models and forecasts, and to better support environmental management actions.
TL;DR: Of the 21 most common coral taxa, 11, including major contributors to coral cover such as Porites and Acropora, showed declines in their sensitivity, and 1 taxon, Acanthastrea, was more sensitive to the exposure in 2016 than in 1998, while 2 taxa showed either little or weak evidence for change in sensitivity.
Abstract: The 1998 and 2016 thermal anomalies were among the 2 most severe global-scale anomalies in recent history, with broad-scale impacts on reef condition. In 2 Kenyan fully protected national park reef lagoons, the water flow, light, and temperature exposure severity of these 2 events was grossly similar at 7.3 cm s–1, ~50 Einsteins m−2 d−1 and ~85 degree-days above summer baseline. Yet, despite similarities in the coral communities’ metrics over this time, the bleaching responses were diminished considerably across this 17 yr period. For example, the numbers of pale and bleached colonies declined from 73 to 27% and from 96 to 60% in the low and high thermal exposure reefs, respectively. A metric that weights bleaching by the intensity of the response and the number of individuals of each taxon also found a decline from 35 to 10% and from 65 to 33%. Of the 21 most common coral taxa, 11, including major contributors to coral cover such as Porites and Acropora, showed declines in their sensitivity. Ten taxa, including Montipora and Pocillopora, showed either little or weak evidence for change in sensitivity, and 1 taxon, Acanthastrea, was more sensitive to the exposure in 2016 than in 1998. Sampling limitations and qualitative differences in the pre-peak temperature conditions did not allow separating the influences of genetic adaptation, acclimatization, and community change.
TL;DR: 41e Congres de the Commission Internationale pour l’Exploration Scientifique de la Mer Mediterranee (CIESM) 12-16 September 2016, Kiel.-- 1 page, 2 figures
Abstract: 41e Congres de la Commission Internationale pour l’Exploration Scientifique de la Mer Mediterranee (CIESM), 12-16 September 2016, Kiel.-- 1 page, 2 figures
TL;DR: The authors thank the University of Western Australia (UWA), Perth, which partly funded this research via an International Postgraduate Research Scholarship and the Australian Institute of Marine Science for their support.
Abstract: We thank the University of Western Australia (UWA), Perth, which partly funded this research via an International Postgraduate Research Scholarship and the Australian Institute of Marine Science. We also thank the Department of Fisheries, the Department of Parks and Wildlife (DPaW) and the Department of Sustainability, Environment, Water, Population and Communities for arranging permits to conduct research at the Scott Reefs and the Rowley Shoals. Thank you also to the crew on board the RV 'Solander'. This research was permitted under UWA Ethics Approvals: RA3/100/1279, RA3/100/1172.
TL;DR: In this article, the authors measured the effectiveness of the MPA network in Belize in promoting increases in fish and coral populations and identified key ecological and environmental factors that influence reef community structure and potentially protection success.
Abstract: A variety of factors have caused the loss of corals and fishes on coral reefs, resulting in ecological, social, and economic consequences for reef ecosystems and the people who depend on them. A widely employed management action to restore reef communities is the implementation of marine protected areas (MPAs). We measured the effectiveness of the MPA network in Belize in promoting increases in fish and coral populations and identified key ecological and environmental factors that influence reef community structure and potentially protection success. From 2009 to 2013, we annually surveyed 16 reefs in Belize, including 8 MPA sites (where ex tractive fishing is limited or prohibited) and 8 unprotected sites. At each site, we quantified the biomass of reef fishes, coral and macroalgal cover, and several biotic and abiotic variables that are known to affect reef inhabitants. High predatory reef fish and parrotfish biomass values were associated with high reef structural complexity and low wave exposure. Mean macroalgal cover was negatively associated with parrotfish biomass in 1 protected zone. However, mean macroalgal cover remained above 40% across all sites, and no change in coral cover was observed during the study. Our results indicate that fisheries restrictions alone do not lead to increases in coral cover even when successful for fishes. We speculate that both illegal and legal fishing may be compromising Belize’s MPA network goals. Furthermore, we suggest that species composition as well as local environmental conditions play key roles in coral reef recovery and should be considered when evaluating management strategies.
TL;DR: In this article, the authors explicitly test how habitat and connectivity interact to shape fish assemblages across estuaries, and find that seagrass is the principal predictor of assemblage composition, an effect that was shaped by spatial connections to other habitats.
Abstract: Estuarine seascapes are a mosaic of habitat types that are connected, to varying degrees, by the movement of organisms. In these seascapes, the attributes of the habitats themselves, as well as the spatial context in which they are embedded, can shape faunal assemblages. Here, we explicitly test how habitat and connectivity interact to shape fish assemblages across estuaries. Our model system comprised 6 distinct estuarine habitats (log snags, mangroves, rocky outcrops, seagrass, sand/mud and urban structures), which represent the full diversity of estuarine habitats and seascape contexts in our study systems. Fish were sampled with cameras at 318 sites in 13 subtropical estuaries in eastern Australia. Habitat type was the principal predictor of fish assemblage composition, an effect that was shaped by spatial connections to other habitats, particularly seagrass beds. Seagrass structured fish assemblages, not only by providing a complex habitat that contained more species and individuals than all other habitats, but also by having a 'footprint' beyond the edge of meadows. Fish were more diverse and abundant in non-seagrass sites that were closer to seagrass meadows. Two other seascape attributes, proximity of sites to the sea and to mangroves, also influenced the composition of fish assemblages, albeit less consistently than distance to seagrass. Conservation and fisheries management programs that seek to enhance or restore fish populations in subtropical estuaries should prioritise seagrass conservation initiatives, which encompass critical ecological linkages with other habitats in estuarine seascapes.
TL;DR: In this paper, the authors analyzed stock assessment output and survey data to test for regimes in the recruitment success of 18 commercially important marine species over a 29-year timespan, and found evidence for three decadal-scale recruitment regimes: low recruitment success in the 1980s, high success in 1990s, and a return to low recruitment performance in the 2000s.
Abstract: There is accumulating evidence for decadal-scale regime shifts at the base of the food web on the Northeast US Continental Shelf. However, less evidence exists for regime shifts in fish recruitment success, particularly for synchronized regimes across multiple species. Here, we analyzed stock assessment output and survey data to test for regimes in the recruitment success of 18 commercially important marine species over a 29 yr timespan. We then tested whether recruitment regimes coincide with regimes in the zooplankton community, and whether the abundance of large spawners could explain the patterns in recruitment. We found evidence for 3 decadal-scale recruitment regimes: low recruitment success in the 1980s, high success in the 1990s, and a return to low recruitment success in the 2000s. This general pattern was found in all datasets of recruitment. The abundance of large spawners did not appear to be a broad-scale driver of recruitment success; however, recruitment regimes coincided with regimes in copepod abundance and size structure.
TL;DR: Noise regulation should be based on frequency-weighted sound levels in addition to broadband levels, to assure that mitigation measures are effective in reducing impact on animals and not only in fulfilling legal requirements.
Abstract: Effects of constructing the DanTysk offshore wind farm (German Bight, 80 turbines, 6 m diameter foundations) were studied by passive acoustic monitoring of pile-driving noise and harbour porpoise Phocoena phocoena echolocation. An acoustic deterrence device (seal scarer) was used to protect porpoises from hearing loss and bubble curtains were used to attenuate the pile-driving noise. Porpoise occurrence, quantified by echolocation signals, decreased when the seal scarer was engaged, during pile driving and up to 5 h after pile driving stopped. This effect extended out to 12 km, less than the 18−25 km reported from other pile drivings performed without bubble curtains. The bubble curtains thus effectively reduced the temporary habitat loss and risk of hearing loss. The 2 bubble curtains each attenuated the noise by between 7 and 10 dB, when used separately, and 12 dB when used together. Attenuation was most pronounced above 1 kHz, where the pile-driving noise at larger distances was comparable to or lower than ambient noise. This suggests that noise regulation should be based on frequency-weighted sound levels in addition to broadband levels, to assure that mitigation measures are effective in reducing impact on animals and not only in fulfilling legal requirements. The strong reaction to the seal scarer raises concern that it may surpass the reactions to the pile-driving noise itself, when operating with bubble curtains, and calls for a re-evaluation of the specifications of seal scarer sounds.
TL;DR: In this paper, the authors examined the effects of the 2011 marine heatwave on benthic macroinvertebrate assemblages in subtidal habitat types (reef "flat" and "slopes" at 4 locations (spanning >800 km of coastline and >6° of latitude) during the period 1999-2015.
Abstract: Extreme climatic events are predicted to increase in severity as a consequence of anthropogenic climate change. In marine ecosystems, the importance of marine heatwaves (MHWs)—discrete periods of anomalously high sea temperatures—is gaining recognition. In 2011, the highest-magnitude MHW ever recorded impacted the west coast of Australia (southeast Indian Ocean). The MHW was associated with widespread mortality of habitat-forming species, including corals and kelps, and structural changes in assemblages of macroalgae and fish. However, the responses of benthic macroinvertebrate assemblages have not yet been fully documented. Here, we resurveyed 2 subtidal habitat types (reef ‘flats’ and ‘slopes’) at 4 locations (spanning >800 km of coastline and >6° of latitude) during the period 1999-2015 to examine the effects of the 2011 MHW on herbivorous macroinvertebrates (i.e. sea urchins, gastropod molluscs). Responses to the MHW varied with latitude; at our warmest study location, abundances were severely depleted, whereas no effects were detected at the coolest location. Across the entire study region, subtle but significant shifts in assemblage structure were observed due to decreased abundances of more southerly-distributed species (i.e. ‘cool’ affinity) and increased abundances of several more northerly-distributed species (i.e. ‘warm’ affinity). The 2011 MHW has had profound effects on the marine biota off the west coast of Australia, across multiple trophic levels and taxonomic groups. Here, as in many other regions, contemporary warming events are superimposed onto gradual warming trends, increasing the likelihood of abrupt changes in ecosystem structure and functioning.
TL;DR: In this paper, the authors showed that CO2 stimulation of primary production enhances the summertime survival, growth, and proliferation of perennial eelgrass Zostera marina from the Chesapeake region, which is regularly impacted by summer heat stress.
Abstract: CO2 is a critical and potentially limiting substrate for photosynthesis of both terrestrial and aquatic ecosystems. In addition to being a climatewarming greenhouse gas, increasing concentrations of CO2 will dissolve in the oceans, eliciting both negative and positive responses among organisms in a process commonly known as ocean acidification. The dissolution of CO2 into ocean surface waters, however, also increases its availability for photosynthesis, to which the highly successful, and ecologically important, seagrasses respond positively. Thus, the process might be more accurately characterized as ocean carbonation. This experiment demonstrated that CO2 stimulation of primary production enhances the summertime survival, growth, and proliferation of perennial eelgrass Zostera marina from the Chesapeake region, which is regularly impacted by summer heat stress. The experiment also quantified the logarithmic response to CO2 in terms of shoot proliferation, size, growth and sugar accumulation that was funda mentally consistent with model predictions based on metabolic carbon balance derived from short-term laboratory experiments performed with other eelgrass populations from cool ocean climates and other seagrass species from tropical and temperate environments. Rather than acting in a neutral fashion or as an independent stressor, increased CO2 availability can serve as a quantitative antagonist to counter the negative impact of climate warming on seagrass growth and survival. These results reinforce the emerging paradigm that seagrasses are likely to benefit significantly from a high-CO2 world.
TL;DR: It is proposed that denticle assemblages in the recent fossil record can help establish quantitative pre-human shark baselines and time-averaged denticles on modern reefs can supplement traditional surveys, which may prove especially valuable in areas where rigorous surveys of sharks are difficult to perform.
Abstract: The last 50 yr of fisheries catch statistics and ecological surveys have reported sig nificant decreases in shark populations, which have largely been attributed to human activities. However, sharks are challenging to census, and this decline likely pre-dated even the longest fishery-dependent time series. Here we present the first use of dermal denticles preserved in reef sediments as a novel tool to reconstruct shark communities. We first built a dermal denticle reference collection and conducted a morphometric analysis of denticle characters to relate denticle form to taxonomy, shark ecology, and denticle function. Denticle morphology was highly variable across the body of an individual shark and between taxa, preventing speciesor genus-level identification of isolated denticles. However, we found that denticle morphology was strongly correlated with shark ecology, and morphometric analysis corroborated existing functional classifications. In a proof of concept, we extracted 330 denticles from modern and fossil reef sediments in Bocas del Toro, Panama and found them to be morphologically diverse and sufficiently well-preserved to allow classification. We observed a high degree of correspondence between the denticles found in the sediments and the sharks documented in the region. We therefore propose that (1) denticle assemblages in the recent fossil record can help establish quantitative pre-human shark baselines and (2) time-averaged denticle assemblages on modern reefs can supplement traditional surveys, which may prove especially valuable in areas where rigorous surveys of sharks are difficult to perform.
TL;DR: In this paper, a combination of long-term onboard server data and a novel data set of high-resolution, remotely sensed vessel tracks (Automatic Identification System [AIS]) was used to reveal progressive divergence of tuna fishing effort, catch, and catch per unit of effort (CPUE) trends in areas adjacent to the reserve from trends in the surrounding fished areas.
Abstract: The largest protected areas of any kind have all recently been established in the ocean. Since 2012, 5 protected areas that exceed 1 million km2 in size have been created, mostly in remote oceanic areas. The potential conservation and fisheries benefits of such reserves have been debated in the public, the media, and the scientific literature. Little is known about their effectiveness for com mercially valuable pelagic predators, especially for highly migratory spe cies such as tuna and billfishes. Here we analyse the iconic Galápagos Marine Reserve, documenting interactions with and changes in associated tuna purse seine fisheries in the Eastern Tropical Pacific. Using a combination of long-term onboard ob server data and a novel data set of high-resolution, remotely sensed vessel tracks (Automatic Identification System [AIS]), we reveal progressive divergence of tuna fishing effort, catch, and catch per unit of effort (CPUE) trends in areas adjacent to the reserve from trends in the surrounding fished areas. Both data sets show a regionally unique hotspot of concentrated effort along the western reserve boundary now receiving >4-fold greater fishing effort density than the rest of the surrounding area. These dynamic interactions of tuna purse seine fisheries with the Galápagos Marine Reserve suggest that the reserve might enhance fish stock availability to local fisheries and help to stabilize local catches despite overall decreasing biomass trends for these highly commercial tuna stocks.
TL;DR: It is clarified that the mechanism by which SGD affects phytoplankton production differs from one ecosystem to another because of variable hydrogeographical properties, such as the type of groundwater discharge (i.e. spring or seepage).
Abstract: Nutrients supplied from submarine groundwater discharge (SGD) are generally thought to enhance primary production in coastal seas. However, there is little evidence for a direct association between SGD and phytoplankton primary productivity. To elucidate the response of in situ primary productivity to SGD, we conducted comparative experiments at 3 coastal sites in Japan with different SGD types (Site A: Obama Bay; Site B: coast along the western foot of Mt. Chokai; Site C: Beppu Bay) during the summers of 2013−2015. At Site A, which is characterized by seepage-type SGD, we found a significant positive relationship between in situ primary productivity and 222Rn concentration. This was likely driven by nutrient-limited water column conditions. On the other hand, at the volcanic coastal Sites B and C, which are dominated by spring-type SGD, no clear relationships between in situ primary productivity and 222Rn concentration were found. Although significant relationships between nutrient concentrations and 222Rn concentration suggest that SGD acts as a primary nutrient source in these regions, the non-trivial influence of light availability complicates those relationships. Furthermore, lower biomass-specific primary productivity around submarine springs at both sites suggests that submarine springs have negative impacts on phytoplankton growth rates around vent sites, possibly due to changes in local environmental conditions. Our study clarified that the mechanism by which SGD affects phytoplankton production differs from one ecosystem to another because of variable hydrogeographical properties, such as the type of groundwater discharge (i.e. spring or seepage).
TL;DR: The acoustic detection rates and diversity of soniferous fish were higher near the mouth and de creased towards the source, suggesting a selection of deeper water and/or more stable water quality conditions for spawning.
Abstract: In this study, our goal was to perform acoustic monitoring of the May River, South Carolina (USA), for a 9 mo period and estimate reproductive timelines for a community of soniferous fishes. Acoustic recorders were deployed to collect sound samples for 2 min, every 20 min at 4 stations from the source to the mouth from February to November 2013. We detected the acoustic presence of 6 fish species: Atlantic croaker Micropogonias undulatus, black drum Pogonias cromis, silver perch Bairdiella chrysoura, oyster toadfish Opsanus tau, spotted sea trout Cynoscion nebulosus, and red drum Sciaenops ocellatus. Acoustic detection rates and diversity of soniferous fish were higher near the mouth and de creased towards the source, suggesting a selection of deeper water and/or more stable water quality conditions for spawning. We estimated the start and end dates of the spawning season and calculated the total hours of chorusing for silver perch, oyster toadfish, spotted seatrout, and red drum. Each species followed a specific seasonal and daily pattern of calling, and we observed synchrony of these calling patterns among stations. For silver perch, oyster toadfish, black drum, and spotted seatrout, a negative tem perature anomaly correlated with decreased calling intensity, while a positive anomaly increased sound production. For oyster toadfish and spotted seatrout, the lunar phase significantly influenced calling. These data serve as a foundation for future studies that are investigating how climate variability may affect seasonal spawning timelines and year class strength of fish populations using passive acoustic monitoring.
TL;DR: It is recommended that researchers refocus efforts towards under-studied regions, taxa and habitats to obtain a more representative understanding of the scales of connectivity and connectivity’s role in maintaining populations.
Abstract: Research into marine population connectivity (MPC)—the rate of transfer of organisms between locations—is important for our understanding of how marine systems operate as well as our ability to conserve them effectively. The large body of research in this field has never been quantitatively assessed to identify the manner in which research effort has been expended. We conducted an extensive quantitative literature review of >1000 studies and analysed the ‘What?’ and the ‘How?’ of MPC research. Publication rates increased dramatically in the mid-2000s, due to a surge of studies utilising genetic techniques and assessing larval dispersal, but studies assessing post-larval movement have not increased at the same rate. The MPC literature is dominated by bony fish, ~3 times more prevalent than the next most common taxonomic class (malacostracan crustaceans). The dispersal of some habitat-forming organisms (e.g. seagrasses, kelps) have been studied extensively (particularly corals), whereas other groups have received minimal attention (e.g. mangroves and saltmarshes). Spatially, studies have been concentrated around Europe, North America and Australia, in contrast to regions such as eastern and southern Asia and western Africa. These taxonomic, habitat and geographic biases are likely to impact our ability to predict and manage for connectivity in these systems due to the large variance in life-history traits and abiotic conditions between well-studied and under studied systems. We recommend that researchers refocus efforts towards under-studied regions, taxa and habitats to obtain a more representative understanding of the scales of connectivity and connectivity’s role in maintaining populations.
TL;DR: Smith et al. as discussed by the authors used seafloor photographic transects to evaluate the distribution and community structure of Antarctic hard-substrate megafauna and the role of dropstones as island habitats in 3 WAP fjords and at 3 nearby shelf stations.
Abstract: The West Antarctic Peninsula (WAP) margin is dominated by glaciomarine fjords and has experienced rapid climate warming in recent de cades. Glacial calving along the peninsula delivers icerafted debris (e.g. dropstones) to heavily sedimented fjord basins and the open continental shelf. Dropstones provide hard substrate, increase habitat heterogeneity, and may function as island habitats surrounded by mud. We used seafloor photographic transects to evaluate the distribution and community structure of Antarctic hard-substrate megafauna and the role of dropstones as island habitats in 3 WAP fjords and at 3 nearby shelf stations. Several lines of evidence indicate that dropstones function as island habitats; their communities adhere to principles of island biogeography theory with (1) a positive correlation between dropstone size and species richness, (2) an increase in the proportion of colonized dropstones with increasing dropstone size, and (3) a species−area scaling exponent consistent with island habitats measured globally. Previous work on the soft-sediment megafauna of this region found strong differences in community composition between fjord and shelf sites, whereas we found that dropstone communities differed within sites at small scales (1 km and smaller). We identified 73 megafaunal morphotypes associated with dropstones, 29 of which were not previously documented in the soft-sediment mega fauna. While dropstones constituted <1% of the total seafloor area surveyed, they contributed 20% of the overall species richness of WAP megabenthos at depths of 437−724 m. WAP dropstone communities adhere to key principles of island biogeography theory, contribute environmental heterogeneity, and increase biodiversity in the WAP region. A rich community of megafauna inhabiting a glacial dropstone in Flandres Bay (400 m), a glaciomarine fjord on the West Antarctic Peninsula. Photo: Dr. Craig R. Smith