Climate-driven changes in abundance and distribution of larvae of oceanic fishes in the southern California region

We examined climatic effects on the geographic distribution and abundance of 34 dominant oceanic fishes in the southern California region using larval fish data collected from the 50‐year long California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys. The oceanic species responses to environmental changes in their geographic distributions were not very pronounced, perhaps because they lived in the deep layer where temperature change was relatively small or because the environmental variation of the CalCOFI region is not strong enough (with an average temperature gradient of the upper 100 m around 91 km °C^?1). Among the 34 taxa, 16 showed a significant distributional shift (median latitude or boundaries) in relation to environmental variables, and eight species significantly shifted their geographic distribution from the 1951–1976 cold period to the 1977–1998 warm period. Interestingly, the vertically migrating taxa more often showed a significant response to environmental variables than the nonmigrating mesopelagic taxa, reflecting the more significant increase in heat content of the upper ocean (<200 m), compared with the deeper zone (300–500 m) where the mesopelagic fishes typically remain. Climate change has significant effects on the abundances of oceanic fishes. Twenty‐four taxa exhibited a significant change in abundance in relation to environmental variables, and 25 taxa, including both warm and cold‐water taxa, showed a significant increase in abundance from the cold to warm period. Analysis of physical data indicated that the surface‐layer (20–200 m) warmed significantly and the isotherms approached shoreward from the cold to the warm period. We further show that the spatial distribution of coastal–neritic fish retreated shoreward and oceanic fish extended shoreward from the cold to warm period. Our results suggest intensified stratification of the southern California region during the warm period may create a suitable habitat for the oceanic species. Moreover, such an unfavorable condition (e.g. changes in food habitat) for coastal–neritic species might result in competitive release for the oceanic fishes to flourish.     

Inter-annual variation in summer zooplankton community structure in Prydz Bay, Antarctica, from 1999 to 2006

Inter-annual variations in zooplankton community structure in Prydz Bay were investigated using multivariate analysis based on samples collected with a 330-μm mesh, 0.5-m² Norpac net during the austral summer from 1999 to 2006. Two distinct communities, an oceanic and a neritic community, were consistently identified in all surveys. Oceanic communities had higher diversity and were indicated by species such as Haloptilus ocellatus, Heterorhabdus austrinus, Thysanoessa macrura, Rhincalanus gigas, Scolecithricella minor and Oikopleura sp.. Neritic communities were indicated by Euphausia crystallorophias and Stephos longipes and were characterized by fewer but more abundant species. In 1999 and 2006, a transitional community was also distinguished near the continental shelf edge, where ice coverage was more extensive than either the oceanic or neritic regions. Significant inter-annual variations in community structure (mainly involving species abundance rather than species composition) were found in both oceanic and neritic communities, being more obvious in the latter. The timing and amplitude of sea ice retreat (polynya appearance), and its effect on food availability, had strong influences on zooplankton community structure. In oceanic communities during years with earlier ice retreat, the extra time available for phytoplankton blooms to accumulate resulted in a higher proportion of large copepods (Calanoides acutus, Calanus propinquus, Metridia gerlachei) (especially the younger copepodites) in the zooplankton assemblage. In neritic communities, zooplankton such as the ice krill E. crystallorophias, and large copepods (C. acutus, C. propinquus, M. gerlachei), also showed higher abundance and earlier developmental stages in years with larger polynya. On the other hand, in years with later ice retreat, smaller polynya, and less time for phytoplankton blooms to form, the abundance of large copepods was lower and older age classes were more common.     

Spring zooplankton distribution and production of the copepod Euterpina acutifrons in Marennes-Oléron Bay (France)

Short term variations of zooplankton populations were studied during an algal spring bloom in two characteristic areas of the Marennes-Oléron Bay (France). The sampling sites were chosen in the north of the bay, one close to the neritic zone, the other close to the estuarine zone. Five distinct zooplanktonic communities were observed: two typical neritic and estuarine assemblages, two eurytopic groups (linked to neritic or estuarine water masses) and an autochtonous community, widely distributed in the north of the bay. The copepod Euterpina acutifrons dominated the zooplankton community during this period of the year in terms of abundance (up to 83% of the zooplankton community). Its production differed between water masses: the highest production occurred at the estuarine station (3.48 ± 0.65 mg C m^–3 d^–1), where nauplii accounted for a large part of these high values. Its P/B ratio was similar at the two stations (0.196 and 0.209 d^–1).     

深远海浮游动物生态学研究进展

深远海浮游生态系统依据水深的差别可以被划分为几个子系统,包括上层、中层、深层和深渊层等。目前大量的研究结果表明在海洋上层,由于光照、温度、海冰和营养盐补充等因素的影响,浮游生物群落往往呈现出显著的时空变化。但在海洋中层及更深的区域,传统观点认为随着水深的增加,海洋的理化环境趋向于稳定,在这一区域生态系统的时空变化要弱于海洋上层。同时受调查技术和经费的限制,人们对于这一广阔区域内浮游生态系统时空变化规律的认识要局限的多。随着我国海洋科学的发展和海洋强国战略的实施,海洋科学研究也逐渐由过去的以近海研究为主发展到当前的近海、边缘海和深远海研究协同发展。但与我国近海浮游生态学过去数十年间积累的大量研究成果相比,我国科学家对深远海,特别是中层、深层和深渊层浮游生态学方面的研究极为缺乏。从大洋浮游动物群落的垂直分布及其变化、种间关系与生态位分化、深海浮游动物群落在碳沉降和生物地球化学循环中的作用等多个角度全面总结了当前国内外深海浮游生态学的研究进展,同时介绍过去十余年来深海浮游生态学研究技术手段上的巨大进步,以期为今后国内同行的研究提供参考和借鉴。     

Composition and spatial variability of macroplankton and micronekton within the Antarctic Polar Frontal Zone of the Indian Ocean during austral autumn 1997

Net sampling and continuous acoustic measurements within the Antarctic Polar Frontal Zone (APFZ) and in the vicinity of the Prince Edward Islands were conducted during austral autumn (April/May) 1997 to describe the composition and distribution of macrozooplankton and micronekton, and to investigate their relations to the prevailing oceanographic regime in the area. Two major circulation patterns associated with the Subantarctic (SAF) and Antarctic Polar (APF) Fronts existed in the oceanic environment surrounding the Prince Edward Islands, promoting high cross-frontal mixing both upstream and downstream of the islands. Average abundance and biomass of macroplankton/micronekton in the top 300-m layer were 21 ind. 1000 m⁻³ and 467 mg DW 1000 m⁻³, respectively. Pelagic crustaceans (euphausiids and amphipods), fish, chaetognaths and gelatinous zooplankton dominated numerically and by biomass. Continuous acoustic measurements displayed elevated pelagic biomass at the SAF and APF. Although four groupings of stations were identified using cluster analysis, a single macroplankton/micronekton community was recognized in the top 300-m layer throughout the offshore area of the APFZ. A modification of the APFZ community was observed within the inter-island region. Subantarctic species dominated zooplankton samples throughout the APFZ, although subtropical species were also well represented at stations occupied in the northern region of the APFZ. A biological response reflected in macroplankton community composition, resulting from an extensive cross-frontal mixing, was observed within the APFZ around the Prince Edward Islands. Accepted: 27 November 1999     

The zooplankton community structure in relation to its biological and physical environment on the Faroe shelf, 1989-1997

The Faroe shelf water is separated from the offshore water by a persistent tidal front, which surrounds the islands. This shelf water contains a neritic zooplankton community, which, regarding species composition, production, seasonal development and environmental conditions, is quite different from that in the surrounding ocean. While during spring and summer the zooplankton in the oceanic environment are dominated by the copepod Calanus finmarchicus, the zooplankton in the shelf water are largely dominated by neritic copepods, mainly Acartia longiremis and Temora longicornis. Calanus finmarchicus occurs in interannually highly variable abundance in the Faroe shelf ecosystem. Meroplanktonic larvae, mainly Balanus spp, and decapod larvae, are also common in the shelf water during spring and summer. During the period presented (1989-1997), the Faroe shelf ecosystem has undergone very large changes in abundance of different zooplankton species. The midsummer abundance of C.finmarchicus, which originally is advected into the shelf from the open ocean, fluctuated from 400 copepods m^-3 in 1989 to 25 copepods m^-3 in 1994, and at the same time the neritic zooplankton increased from 120 m^-3 in 1989 to 450 m^-3 in 1994. Consequently, the midsummer biomass in the shelf fluctuated by a factor of 10 during the same period. It is presumed that this variability between oceanic- and neritic-dominated zooplankton, their sizes and their biomass has greatly affected the entire pelagic ecosystem.      

渤海浮游动物群落生态特点Ⅰ.种类组成与群落结构

以１９５９年全国海洋普查浮游动物中网周年标本为材料,对渤海浮游动物的群落结构进行分析。渤海浮游动物群落以近岸广温种为主,主要优势种包括小拟哲水蚤（Ｐａｒａｃａｌａｎｕｓ ｐａｒｖｕｓ）、双毛纺锤水蚤（Ａｃａｒｔｉａ ｂｉｆｉｌｏｓａ）、强额拟哲水蚤（Ｐａｒａｃａｌａｎｕｓ ｃｒａｓｓｉｒｏｓｔｒｉｓ）、拟长腹剑水蚤（Ｏｉｔｈｏｎａ ｓｉｍｉｌｉｓ）、墨氏胸刺水蚤（Ｃｅｎｔｒｏｐａｇｅｓ ｍｃｍｕｒ     

Community structure of pelagic cnidarians off Adélie Land, East Antarctica, during austral summer 2008

Some studies have suggested that pelagic cnidarians are important components of the Southern Ocean ecosystem due to their high abundance and diversity and their high predatory effects, although little information on these animals is available. Thus, we examined the spatial distribution of pelagic cnidarians from the oceanic to neritic zone off Adélie Land, East Antarctica. Discrete depth sampling was conducted from the surface to 2,000 m depth from late January to early February 2008. In total, 3347 individuals representing 45 species/taxa from eight orders were collected. Cluster analysis revealed three major clusters: (1) an epipelagic group in the oceanic zone composed mainly of Pegantha martagon, the abundance and species diversity of which were very low; (2) a meso- and bathy-pelagic group characterised by high abundance and species diversity with dominance of Dimophyes arctica, Vogtia serrata, and Halicreas minimum; and (3) a neritic group represented by a high abundance of Diphyes antarctica. Cnidarian communities in the epipelagic zone were divided by hydrographic structures such as the Southern Boundary of the Antarctic Circumpolar Current and Antarctic Slope Front, whereas those in the meso- and bathy-pelagic layers dominated by circumpolar deep water were relatively stable with higher diversity throughout the oceanic zone.     

The inshore marine ecosystem off the Vestfold Hills,Antarctica

The planktonic, ice/water interface, and benthic communities at three sites off the coast of the Vestfold Hills, Antarctica, were examined over a complete year.The planktonic flora and fauna were composed predominantly of oceanic species with diatoms and copepods the numerically dominant groups. Primary production was largely restricted to the summer months except for epontic algae which developed in spring. The zooplankton exhibited a similar seasonal cycle but lagged some months behind that of the phytoplankton.The ice/water interface (epontic) fauna consisted of species from the plankton and benthos. Copepods were major contributors; however, two amphipod species dominated. Seasonality of the fauna in this habitat was determined by ice formation and breakout, and development of ice algae.Each of the benthic substrates supported a characteristic macrofaunal assemblage, although infaunal amphipods and tanaids were similar at each site. Infauna exhibited a distinct seasonal cycle related to that of the primary producers whereas macrofauna showed no seasonal changes in abundance.Species composition of each community in this coastal antarctic region was comparable with that of similar habitats in other antarctic coastal areas, supporting the circumpolarity of antarctic marine communities.     

Vertical gradients in species richness and community composition across the twilight zone in the North Pacific Subtropical Gyre

Although metazoan animals in the mesopelagic zone play critical roles in deep pelagic food webs and in the attenuation of carbon in midwaters, the diversity of these assemblages is not fully known. A metabarcoding survey of mesozooplankton diversity across the epipelagic, mesopelagic and upper bathypelagic zones (0–1500 m) in the North Pacific Subtropical Gyre revealed far higher estimates of species richness than expected given prior morphology‐based studies in the region (4,024 OTUs, 10‐fold increase), despite conservative bioinformatic processing. Operational taxonomic unit (OTU) richness of the full assemblage peaked at lower epipelagic–upper mesopelagic depths (100–300 m), with slight shoaling of maximal richness at night due to diel vertical migration, in contrast to expectations of a deep mesopelagic diversity maximum as reported for several plankton groups in early systematic and zoogeographic studies. Four distinct depth‐stratified species assemblages were identified, with faunal transitions occurring at 100 m, 300 m and 500 m. Highest diversity occurred in the smallest zooplankton size fractions (0.2–0.5 mm), which had significantly lower % OTUs classified due to poor representation in reference databases, suggesting a deep reservoir of poorly understood diversity in the smallest metazoan animals. A diverse meroplankton assemblage also was detected (350 OTUs), including larvae of both shallow and deep living benthic species. Our results provide some of the first insights into the hidden diversity present in zooplankton assemblages in midwaters, and a molecular reappraisal of vertical gradients in species richness, depth distributions and community composition for the full zooplankton assemblage across the epipelagic, mesopelagic and upper bathypelagic zones.     

The summer zooplankton community at South Georgia: biomass,vertical migration and grazing

Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m^–2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times higher than values generally reported for the Southern Ocean and may reflect firstly, the high productivity of the study area, secondly, the time of year, summer, when biomass for many species is maximal, and thirdly, the high sampling efficiency of the LHPR. Principal components analysis disclosed similarities and differences between adjacent depth strata in terms of abundance, biomass and species composition. At both stations most variability occurred in the mixed layer (0–60 m) and thermocline (60–120 m) with depth horizons below this being more homogeneous. Diel migrations were observed for most taxa with abundance increasing in the mixed layer at night. At the oceanic station, species and higher taxa belonging to the mesopelagic community were generally well spread throughout this domain and, with the exception of Pleuromamma robusta and Metridia curticauda, showed little evidence of migration. The grazing impact of the epipelagic community (copepods and small euphausiids) was estimated to remove 3–4% of the microbial standing stock day^–1 and a conservative 25% and 56% of daily primary production at the oceanic and shelf stations respectively.     

Copepod communities related to water masses in the southwest East China Sea

The East China Sea is characterized by a complex hydrographic regime and high biological productivity and diversity. This environmental setting in particular challenged a case study on the use of mesozooplankton community parameters as indicators of water masses. In order to reveal spatial patterns of zooplankton communities during summer, a large scale oceanic transect study was conducted. Two transects were taken in the southwest East China Sea region, covering for the first time the China shelf, slope, and the estuaries of the Yangtze river and of the Minjiang river, the northern Taiwan Strait, and the Kuroshio Current region. A total of 77 copepod species were quantified. Copepod abundance was significantly higher in the estuary of the Yangtze River runoff mixture waters and lowest at the Kuroshio Current Region. The calanoid Parvocalanus crassirostris was the most frequently occurring and abundant species retrieved from 27 samples of a total of 39 samples. The use of multivariate cluster analysis separated the Mainland China Shelf from the northern Taiwan Strait and the Kuroshio Current Region at the first hierarchical level. The use of an indicator value method (IndVal) associated with each cluster of stations revealed characteristic species assemblages. Two hierarchical levels defined 4 assemblages within geographical sectors representing copepod assemblages of the Kuroshio Current Region, of the northern Taiwan Strait and the southern China Shelf near the estuary of the Minjiang River and northern stations near the estuary of the Yangtze River. Overall, there was a strong correspondence between the distribution of certain copepod species and water masses. Differences between the Mainland China shelf, the northern Taiwan Strait and the Kuroshio Current Region were characterized by differences in species composition and abundance. Water mass boundaries in the study area were exclusively indicated by distinct differences in species composition, emphasizing a correlation between copepod communities and water masses of the southwest East China Sea in summer.     

Distribution and abundance dynamics of jellyfish in the Sea of Okhotsk

The seasonal and interannual trends in the distribution and abundance of jellyfish (Scyphozoa and Hydrozoa) in the epipelagic and mesopelagic areas of the Sea of Okhotsk during 1992–2005 were examined on the basis of trawl survey data. The area of occurrence, biomass, and the numbers of Scyphozoa in the epipelagic layer were the smallest in spring; in summer and fall their abundance sharply increased and then decreased in winter. In contrast to the epipelagic zone, the numbers of scyphomedusae in the mesopelagic layer were significantly lower in the summer than in the winter and spring. This probably indicates that a part of scyphomedusae winter in the mesopelagic. Hydrozoa in both the epi- and mesopelagic areas were more numerous in the winter and spring. Jellyfish biomass and abundance greatly changed from year to year. Thus, in fall the biomass of scyphomedusae and hydromedusae in the epipelagic zone varied from 166 to 1271 and from 6 to 49 kg/km², respectively.     

Evolution saisonniere du zooplancton dans trois sites peu profonds de Thau,une lagune Nord-Mediterraneenne

A monthly zooplankton survey has been conducted from March 1982 to March 1983 at three shallow stations of Thau, a northern-mediterranean lagoon. These stations differ by their distance from the entry of sea-water in the lagoon. Parameters such as pH, temperature, dissolved oxygen, conductivity and turbidity have been measured simultaneously with the sampling in the same water layer. The zooplankton collected corresponds to species usually found in marine neritic communities. In the spring, species richness is maximum. During the summer, meroplankton forms dominant populations in the communities. Autumn is marked by a reduction of the number of species and of the abundance in both components, holoplankton and meroplankton. Few species are present in the winter holoplankton while meroplankton disappears practically from the samples. The sites under observation are subjected to unpredictable changes, in water movement as well as in the organization of the zooplankton communities. These modifications are strongly influenced by weather conditions.     

Seasonal strengths of the abiotic and biotic drivers of a zooplankton community

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Spatial structure of the zooplankton community in the Cabo Frio region (Brazil) influenced by coastal upwelling

Cabo Frio area (Central-southern Brazilian littoral) is characterized by a coastal upwelling due to prevailing E-NE winds, mainly during the spring-summer season. The geographic distribution of the zooplankton was described in order to separate ecological areas in terms of specific communities. Cluster analysis by weighted pair-group method (WPGA) and principal component (PC) analysis was performed on the most important hydrological parameters and zooplankton taxa. The first PC, explaining 38% of the total zooplankton variability, represented the influence of the nearshore-offshore gradient. Zooplankton communities and ecological areas were defined as follows:

1. nearshore neritic: the richest region with more than 5 000 org. m-3. In this very narrow nearshore region we observed 3 groups of taxa deliminated by upwelling effects and trophic conditions: a) Ctenocalanus vanus, Penilia avirostris, Calanoides carinatus and Copepod larva, all herbivorous species associated with the phytoplankton blooms in the upwelling zone; b) Creseis acicula and Temora stylifera; c) Siphonophora, Chaetognaths and a high diversity of Copepoda dominated by Coryceus amazonicus, C. giesbrechti, Eucalanus pileatus, Clausocalanus acuicornis, all carnivorous or omnivorous feeders representing a high degree of complexity of the ecosystem.
2. offshore neritic: characterized by appendicularians, this region constitutes an intermediate zone between coastal and oceanic waters.
3. oceanic: occupied by the Brazil Current where zooplankton is poor, but diversified, with typical copepods from tropical warm water: Clausocalanus furcatus, Mecynocera clausi, Corycella gracilis, Oithona setigera, Coryceus typicus, Oncea conifera, Undinula vulgaris, Calocalanus pavo, Haloptilus longicornis, Lucicutia flavicornis.

     

Spatio-temporal variations of the zooplankton abundance and composition in a West African tropical coastal lagoon (Grand-Lahou,Côte d’Ivoire)

Zooplankton constitutes a sensitive tool for monitoring environmental changes in coastal lagoons; however, the available information on zooplankton communities is not sufficient to optimize their rational management. The relationships between zooplankton distribution and environmental factors were studied in a tropical lagoon to test whether the indicator properties of zooplankton assemblages could be used to monitor water quality, in a context of expected eutrophication provoked by an increasing anthropogenic activity. Twenty-one (21) stations were sampled monthly from January to December 2004. The community was composed of 65 taxa including Copepoda, Rotifera, and Cladocera. Copepoda was the most abundant group (81% of total numbers). The main zooplankton species were Oithona brevicornis, Acartia clausi, and Brachionus plicatilis. The highest zooplankton abundance (171–175 ind. l⁻¹) was recorded during the long, dry season (February–April) and the lowest (40–45 ind. l⁻¹) during the rainy and the flood periods (June–July). At a spatial level, the lowest abundance was observed in the estuarine zone. During the dry seasons (December–April and August–September), marine zooplankton taxa were abundant near the channel of Grand-Lahou, and brackish water taxa dominated in the other sites. Multivariate analyses (Co-inertia) showed that the composition of zooplanktonic communities and their spatio-temporal variations were mainly controlled by salinity variations closely linked to the climatic and hydrological context. The role of the trophic state on zooplankton communities could not be clearly evidenced. Our results and a comparison with previous studies in the neighboring, highly polluted Ebrié Lagoon suggest that the ratio between Oithona and Acartia abundance could be used as biological indicator for the water quality. Handling editor: S. I. Dodson     

Distribution and abundance of hyperiid amphipods in relation to summer mesoscale features in the southern Gulf of Mexico

Seventy-one hyperiid species were identified from 97 zooplanktonsamples collected in the southern Gulf of Mexico during July1988. About 91% of the adult individuals belonged to five species:Lestrigonus bengalensis (86.56% of total hyperiid numbers),Anchylomera blossevillei (1.20%), Phronimopsis spinifera (1.05%),Hyperioides longipes (1.00%) and Hyperietta vosseleri (0.99%).Overall, up to 74% of the hyperiids were collected at night,although a reverse migration was observed in the anticyclones.The mean abundance was 5-fold higher at the neritic stationsthan in the oceanic areas. This tendency was even more markedat night. Night samples yielded about the same number of speciesas during the daytime (56 taxa versus 61). Four mesoscale features(two anticyclones, one cyclone and one upwelling) characterizedthe oceanic mesoscale circulation in the surveyed area. Theabundance of the oceanic hyperiid community showed significantdifferences related to some of the mesoscale features activein the area, i.e. the abundance in the Lazy Eddy anticyclonewas lower than that in the cyclone (day and night). Overall,the upwelling areas showed a tendency to have higher abundancesthan the downwelling features (anticyclones). Cluster analysisindicated neritic–oceanic differences rather than mesoscalefeature-related differences in the local hyperiid community.The neritic community showed differences that were attributedto the effect of upwelling. The summer and spring hyperiid communitieshad important differences in the same area, thus suggestinga seasonal succession of the gulf hyperiid community.     

Zooplankton annual cycle in a Mediterranean coastal area

The annual cycle of the zooplankton community in the SaronikosGulf (Aegean Sea, Greece) was studied over a period of 2 years.The sampling scheme included monthly hauls at three stationsdifferentiated according to depth and neritic character. Maximumvalues of total zooplankton abundance were found in summer monthsup to early autumn and partially in spring. Copepods dominatedduring most of the year (Clausocalanus furcatus, Paracalanusparvus, Temora stylifera, Ctenocalanus vanus, Oithona similis,Oithona plumifera), while cladocerans (Penilia avirostris) wereabundant in summer months and in September. No important fluctuationswere detected between the 2 years of study, while monthly oneswere more significant in the more neritic station during thewinter–spring period. Correspondence analysis showed thatthe seasonal evolution of zooplankton is related to environmentalparameters: temperature, hydrography expressed in open sea influenceand topography.