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Journal ArticleDOI

Changes in biodiversity of phytoplankton, zooplankton, fishes and macrobenthos in the Southern Caspian Sea after the invasion of the ctenophore Mnemiopsis Leidyi

01 Jul 2010-Biological Invasions (Springer Netherlands)-Vol. 12, Iss: 7, pp 2343-2361
TL;DR: Monitoring for 6 years showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton, and some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophile.
Abstract: Monitoring for 6 years (2001–2006) showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton. While this decline appeared to have reduced the nourishment of sprat (also known as kilka), it seemed to have affected phytoplankton favorably mainly due to the decrease in grazing pressure. During 2001–2002, when M. leidyi abundance and biomass were at their highest levels, abundance of dinoflagellates and cyanophytes exceeded that of diatoms. Before the invasion (1996) and in some years after the invasion (2003, 2004 and 2006) diatom abundance was higher than the abundance of other groups. In September 2005, an unprecedented bloom of the toxic cyanophyte Nodularia sp. was observed in the southern Caspian Sea. Disappearance of edible zooplankton such as Eurytemora spp. was among the first changes observed after the expansion of M. leidyi in the area. Some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophore. While the biomass of some deposit feeders, such as the polychaete Nereis diversicolor and oligochaete species increased, benthic crustaceans decreased sharply in abundance during 2001–2003 and completely disappeared during 2004–2006. Iranian catches of kilka, the most abundant and widespread zooplanktivorous fish, decreased significantly in the southern Caspian Sea after 1999. Iranian landings of kilka dropped ~70% from 69,070 ± 20,270 t during 1995–2000 to 23,430 ± 12,240 t during 2001–2006, resulting in a loss of at least 125 million US dollars to the economy. There were also changes in the total catches of large predators such as the kutum and mullet, which mainly feed on kilka, between 1991 and 2006.
Citations
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Journal ArticleDOI
TL;DR: Of the 66 LMEs defined thus far that cover the world’s coastal waters and seas, trends of jellyfish abundance after 1950 (increasing, decreasing, or stable/variable) were identified for 45, with variable degrees of confidence.
Abstract: Although there are various indications and claims that jellyfish (ie, scyphozoans, cubozoans, most hydrozoans, ctenophores, and salps) have been increasing at a global scale in recent decades, a rigorous demonstration of this has never been presented Because this is mainly due to scarcity of quantitative time series of jellyfish abundance from scientific surveys, we attempt to complement such data with non-conventional information from other sources This was accomplished using the analytical framework of fuzzy logic, which allows the combination of information with variable degrees of cardinality, reliability, and temporal and spatial coverage Data were aggregated and analyzed at the scale of Large Marine Ecosystem (LME) Of the 66 LMEs defined thus far that cover the world’s coastal waters and seas, trends of jellyfish abundance after 1950 (increasing, decreasing, or stable/variable) were identified for 45, with variable degrees of confidence Of those 45 LMEs, the majority (28 or 62%) showed increasing trends These changes are discussed in the context of possible sources of bias and uncertainty, along with previously proposed hypotheses to explain increases in jellyfish

374 citations

Journal ArticleDOI
TL;DR: Newly sequenced transcriptomes are combined with existing data to establish Ctenophora as the sister group to all other animals and suggest a radiation around 350 Ma as well as multiple transitions from a pelagic to benthic lifestyle within ctenophores.
Abstract: Ctenophora, comprising approximately 200 described species, is an important lineage for understanding metazoan evolution and is of great ecological and economic importance. Ctenophore diversity includes species with unique colloblasts used for prey capture, smooth and striated muscles, benthic and pelagic lifestyles, and locomotion with ciliated paddles or muscular propulsion. However, the ancestral states of traits are debated and relationships among many lineages are unresolved. Here, using 27 newly sequenced ctenophore transcriptomes, publicly available data and methods to control systematic error, we establish the placement of Ctenophora as the sister group to all other animals and refine the phylogenetic relationships within ctenophores. Molecular clock analyses suggest modern ctenophore diversity originated approximately 350 million years ago ± 88 million years, conflicting with previous hypotheses, which suggest it originated approximately 65 million years ago. We recover Euplokamis dunlapae—a species with striated muscles—as the sister lineage to other sampled ctenophores. Ancestral state reconstruction shows that the most recent common ancestor of extant ctenophores was pelagic, possessed tentacles, was bioluminescent and did not have separate sexes. Our results imply at least two transitions from a pelagic to benthic lifestyle within Ctenophora, suggesting that such transitions were more common in animal diversification than previously thought. Newly sequenced transcriptomes are combined with existing data to establish Ctenophora as the sister group to all other animals and suggest a radiation around 350 Ma as well as multiple transitions from a pelagic to a benthic lifestyle.

183 citations

Journal ArticleDOI
TL;DR: The foundations of the ctenophore’s invasive success, which include the source-sink dynamics that characterize Mnemiopsis populations in temperate coastal waters, are reviewed, and the variables most likely to determine whether introduction of Mnemiops to a novel community results in an inconspicuous addition or a disruptive invasion are reviewed.
Abstract: The genus Mnemiopsis is comprised of a single species, Mnemiopsis leidyi A. Agassiz, 1865, that has recently made the transition from a distribution limited to the Atlantic coasts of North and South America to an invasive range that includes the Black, Caspian, Mediterranean, North, and Baltic seas. We review the foundations of the ctenophore’s invasive success, which include the source-sink dynamics that characterize Mnemiopsis populations in temperate coastal waters where the ctenophore achieves its highest biomass levels and ecosystem impacts. Within its native temperate range, Mnemiopsis is frequently a dominant, seasonal, colonizing species with limited dispersal capacities. Cross-oceanic transport within ballast waters of intercontinental shipping vessels has altered this dispersal limitation and initiated a rapid global spread of Mnemiopsis. Owing to continuing transport via transoceanic shipping, we anticipate continued range expansion and review the variables most likely to determine whether introduction of Mnemiopsis to a novel community results in an inconspicuous addition or a disruptive invasion.

106 citations


Cites background from "Changes in biodiversity of phytopla..."

  • ...The dramatic effects following Mnemiopsis introductions documented in the Black (e.g., Kideys, 2002; Shiganova et al., 2004a) and Caspian (e.g., Shiganova et al., 2004b; Roohi et al., 2008, 2009) seas occurred in habitats that lacked gelatinous predators (Purcell et al., 2001)....

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  • ...Mnemiopsis introductions have been comparatively devastating in regions without other gelatinous predators, such as the Caspian sea (Roohi et al., 2008, 2009), but they may be moderated in the presence of established indigenous gelatinous predators, such as in recently invaded European regions…...

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Journal ArticleDOI
TL;DR: It is demonstrated that the predatory success of the lobate ctenophore Mnemiopsis leidyi lies in its use of cilia to generate a feeding current that continuously entrains large volumes of fluid, yet is virtually undetectable to its prey.
Abstract: In contrast to higher metazoans such as copepods and fish, ctenophores are a basal metazoan lineage possessing a relatively narrow set of sensory-motor capabilities. Yet lobate ctenophores can capture prey at rates comparable to sophisticated predatory copepods and fish, and they are capable of altering the composition of coastal planktonic communities. Here, we demonstrate that the predatory success of the lobate ctenophore Mnemiopsis leidyi lies in its use of cilia to generate a feeding current that continuously entrains large volumes of fluid, yet is virtually undetectable to its prey. This form of stealth predation enables M. leidyi to feed as a generalist predator capturing prey, including microplankton (approximately 50 μm), copepods (approximately 1 mm), and fish larvae (>3 mm). The efficacy and versatility of this stealth feeding mechanism has enabled M. leidyi to be notoriously destructive as a predator and successful as an invasive species.

84 citations


Cites background from "Changes in biodiversity of phytopla..."

  • ...Its arrival in each of these regions has led to decreased zooplankton abundances and diversity (7–10), often with trophic cascades that increase phytoplankton standing stocks (10, 11)....

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Journal ArticleDOI
TL;DR: In this article, the authors conducted a multi-year field study to investigate plankton dynamics in the Lower Columbia River Estuary (LCRE), and conducted monthly sampling of the mesozooplankton (> 73 μm) at a station near Astoria, Oregon.
Abstract: As part of a multi-year field study to investigate plankton dynamics in the Lower Columbia River Estuary (LCRE), we conducted monthly sampling of the mesozooplankton (> 73 μm) at a station near Astoria, Oregon. The planktonic copepod community was numerically dominated by three non-indigenous species (NIS), Pseudodiaptomus forbesi, Limnoithona tetraspina, and Sinocalanus doerrii, and two native species, Eurytemora affinis and Diacyclops thomasi. However, seasonal co-occurrence of non-indigenous and native copepods was highly variable between species-pairs. The native E. affinis and the non-indigenous S. doerrii showed the greatest temporal overlap (March-October), but other species-pairs also showed periods of considerable overlap during some seasons (e.g., E. affinis and P. forbesi in June-September). Spatial co-occurrence of native and non-indigenous species was also examined in temperature and salinity “space” (rather than geographic space): all six species-pairs (3 non-indigenous species × 2 native species) showed some degree of overlap, with the greatest (proportional) overlap occurring between the native E. affinis and the two nonindigenous species, S. doerrii and P. forbesi. This suggests the potential for competition to occur between native and non-native copepods in the LCRE, although with variation between seasons and species. Future studies are recommended that explicitly test for and distinguish between the relative importance of biological (e.g., competition and predation) and physico-chemical processes (e.g., freshwater runoff, eutrophication) in regulating the population dynamics of native and invasive copepods in the LCRE.

43 citations


Cites background from "Changes in biodiversity of phytopla..."

  • ...These plankton invaders can have profound ecological and economic impacts, the most notorious and well-studied being the ctenophore Mnemiopsis leidyi (Agassiz, 1865) in the Black and Caspian Seas (Shiganova et al. 2004; Daskalov and Mamedov 2007; Roohi et al. 2008; Roohi et al. 2010)....

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  • ...These plankton invaders can have profound ecological and economic impacts, the most notorious and well-studied being the ctenophore Mnemiopsis leidyi (Agassiz, 1865) in the Black and Caspian Seas (Shiganova et al. 2004; Daskalov and Mamedov 2007; Roohi et al. 2008; Roohi et al. 2010)....

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References
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Journal ArticleDOI
TL;DR: A set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera are presented and designed to minimize the effort of microscopic measurement.
Abstract: Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co-occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.

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"Changes in biodiversity of phytopla..." refers methods in this paper

  • ...The volume of each cell was calculated by measuring its diameter, length and width (Senichkina 1986; Hillebrand et al. 1999)....

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TL;DR: This paper presents the results of a large-scale study of sampling and experimental design of Zooplankton dynamics in response to the prokaryoticarming crisis in the Southern Ocean.
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TL;DR: Over recent decades, man's expanding influence on the oceans has begun to cause real change and there is reason to think that in some regions, new blooms of jellyfish are occurring in response to some of the cumulative effects of these impacts.
Abstract: By the pulsed nature of their life cycles, gelatinous zooplankton come and go seasonally, giving rise in even the most undisturbed circumstances to summer blooms. Even holoplanktonic species like ctenophores increase in number in the spring or summer when planktonic food is available in greater abundance. Beyond that basic life cycle-driven seasonal change in numbers, several other kinds of events appear to be increasing the numbers of jellies present in some ecosystems. Over recent decades, man’s expanding influence on the oceans has begun to cause real change and there is reason to think that in some regions, new blooms of jellyfish are occurring in response to some of the cumulative effects of these impacts. The issue is not simple and in most cases there are few data to support our perceptions. Some blooms appear to be long-term increases in native jellyfish populations. A different phenomenon is demonstrated by jellyfish whose populations regularly fluctuate, apparently with climate, causing periodic blooms. Perhaps the most damaging type of jellyfish increase in recent decades has been caused by populations of new, nonindigenous species gradually building-up to ‘bloom’ levels in some regions. Lest one conclude that the next millennium will feature only increases in jellyfish numbers worldwide, examples are also given in which populations are decreasing in heavily impacted coastal areas. Some jellyfish will undoubtedly fall subject to the ongoing species elimination processes that already portend a vast global loss of biodiversity. Knowledge about the ecology of both the medusa and the polyp phases of each life cycle is necessary if we are to understand the true causes of these increases and decreases, but in most cases where changes in medusa populations have been recognized, we know nothing about the field ecology of the polyps.

661 citations


"Changes in biodiversity of phytopla..." refers background in this paper

  • ...Overfishing, eutrophication and global warming have also been suggested as triggering factors for explosions in both native and introduced waters ( Mills 2001; Lynam et al. 2006; Bilio and Niermann 2004; Purcell 2005)....

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  • ...Overfishing, eutrophication and global warming have also been suggested as triggering factors for explosions in both native and introduced waters (Mills 2001; Lynam et al. 2006; Bilio and Niermann 2004; Purcell 2005)....

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01 Jan 1974
TL;DR: Rodent distribution and abundance in relation to season, habitat, and cover solely in agricultural habitats of Vigo County, Indiana was investigated in this paper, and the specific objective of this report is to relate those findings to explain the occurrence of these rodents in cultivated field ecosystems and to compare their results with those of previous studies to determine what changes, if any, have occurred in the distribution and abundances of these animals in cultivated fields.
Abstract: rodent distribution and abundance in relation to season, habitat, and cover solely in agricultural habitats of Vigo County, Indiana. The specific objective of this report is to relate those findings to explain the occurrence of these rodents in cultivated field ecosystems and to compare my results with those of previous studies to determine what changes, if any, have occurred in the distribution and abundance of these rodents in cultivated field ecosystems.

648 citations

Journal ArticleDOI
TL;DR: In eleven species studied from subtropical, temperate and subarctic environments, warm temperatures were related to large population sizes; three scyphozoan species in the North Sea, and one mesopelagic hydromedusan were exceptions to that trend.
Abstract: Much speculation and some evidence suggest that jellyfish and ctenophore populations have increased in recent decades. Unfortunately, few past records exist with which to compare current populations, and our knowledge of how environmental factors affect jellyfish population size is meagre. Human enterprise has wrought many changes in the ocean that are hypothesized to favour jellyfish, including eutrophication, reduction of fish stocks, and global warming. In addition to anthropogenic changes, natural climate cycles may affect jellyfish populations. Records of jellyfish and ctenophore abundance that appear to be related to indices of climate variations (temperature, salinity, North Atlantic Oscillation, North Pacific Decadal Oscillation, El Nino Southern Oscillation) are reviewed. In eleven species studied from subtropical, temperate and subarctic environments, warm temperatures were related to large population sizes; three scyphozoan species in the North Sea, and one mesopelagic hydromedusan were exceptions to that trend. One tropical scyphomedusan species was decimated by unusually warm, salty El Nino conditions in Palau. Because climate changes have complex ecosystem-level effects, the proximate causes of jellyfish increases are difficult to deduce. Therefore, the effects of temperature, salinity and prey on asexual production of new medusae from the benthic polyps of scyphomedusae and hydromedusae also are reviewed. Experiments on temperate species show greater and more rapid production of medusae at warmer temperatures. Salinity also had significant effects, and was especially important for estuarine species. Temperature and salinity affect asexual reproduction rates directly through metabolism, and indirectly through prey capture. Ocean warming may shift the distributions, expand the seasonal occurrence, and increase the abundances of temperate-boreal species. Populations living near their thermal maximum may suffer negative consequences of warming.

468 citations


"Changes in biodiversity of phytopla..." refers background in this paper

  • ...Overfishing, eutrophication and global warming have also been suggested as triggering factors for explosions in both native and introduced waters (Mills 2001; Lynam et al. 2006; Bilio and Niermann 2004; Purcell 2005)....

    [...]