Climate-mediated changes in zooplankton community structure for the eastern Bering Sea

Interannual summer variability in euphausiid populations on the eastern Bering Sea shelf during the recent cooling event (2008–2010)

In the Eastern Bering Sea, changes in sea ice have been implicated in recent major upper‐trophic level shifts. However, the underlying relationships between sea ice and primary producers have not been well tested. Here, we combine data from multiple satellite platforms, reanalysis model results and biophysical moorings to explore the dynamics of spring and summer primary production in relation to sea ice conditions. In the northern Bering Sea, sea ice consistently retreated in late spring, leading to ice‐edge phytoplankton blooms in cold (0–1 °C) waters. However, in the southeastern Bering Sea, sea ice retreat was far more irregular. Although this did not significantly alter bloom timing, late retreat led to blooms at the ice‐edge while early retreat led to blooms in open waters that were warmer (≤5.4 °C) and >70% more productive. Early sea ice retreat also led to higher productivity in summer, likely due to weaker thermal stratification. Overall, annual net primary production during warm years of early sea ice retreat was enhanced by 40–50% compared to years with late sea ice retreat in the southeastern Bering Sea. These findings suggest the potential for future sea ice loss to enhance overall carrying capacity of the southeastern Bering Sea ecosystem. Consistently warm blooms in the future may also channel more energy flow toward the pelagic, rather than benthic, environment. To date, however, neither sea ice extent nor the timing of its retreat have undergone long‐term changes in the Eastern Bering Sea.

Latitudinal trends and temporal shifts in the catch composition of bottom trawls conducted on the eastern Bering Sea shelf

Recent shifts in northern Bering Sea snow crab (Chionoecetes opilio) size structure and the potential role of climate-mediated range contraction

Changes in the distribution and abundance of albatrosses in the eastern Bering Sea: 1975–2010

The zooplankton community of Lake Küçükçekmece includes individuals from freshwater groups Rotifera and Cladocera, and also marine species Acartia clausi of the subclass Copepoda; Tintinnopsis nana, Favella sp. Jorgensen, 1924, and Strobilidium spiralis from the group Ciliata; Micronereis sp. Linnaeus, 1758 and Spio sp. Fabricius, 1785 from the class Polychaeta; Pleurobrachia pileus from the phylum Ctenophora; and Gammarus sp. Fabricius, 1775 from the order Amphipoda. Rotifera was the dominant group for each season studied. In autumn, dominant specimens included Bosmina longirostris, Spio sp. Fabricius, 1785, Pleurobrachia pileus, the cypris and nauplius larva of Balanus sp., and veliger larva. In winter, dominant species included Synchaeta pectinata, Filinia longirostris, and Epiphanes sp. Ehrenberg, 1832. In spring, dominate species included Asplanchna priodonta and Strobilidium spiralis. In summer, the dominant species was Brachionus plicatilis. Polyarthra major, Filinia longiseta, Keratella cochlearis, and Brachionus, which were found in the lake, are indicator species of eutrophication. Marine species Tintinnopsis nana peaked during spring at the first and second sampling stations, while Acartia clausi peaked during summer at the second station.

Planktonic foraminiferal biogeography in the Indian sector of the Southern Ocean: Contribution from CPR data

To describe past changes in trophic structure, analyses were conducted of zooplankton (Cladocera, Rotifera) assemblages recovered in a 210 Pb dated sediment core from a shallow brackish lake exposed to several fish kill episodes during the 20 th century. A weighted-averaging zooplankton-based transfer function was applied to infer planktivorous fish densities (PL-CPUE) and to elucidate the potential of identify- ing fish kill incidents using sedimentary subfossils. The stratigraphical record showed a shift during the 20 th century. The cladoceran community structure changed from high abundance of macrophyte-associated taxa and chydorids, characteristic of clear water conditions, towards a community composed mainly by sediment-associated taxa, small-sized pelagic taxa as well as rotifers and chydorids, characteristic of eutrophic turbid conditions. Coinciding with these changes, the mean size of Daphnia ephippia decreased while inferred PL-CPUE increased. The results point towards progressive eutrophication with additional impact of salinity. Reduced temporal resolution of the sediment record made identification of fish kill incidents difficult. The indications of high fish planktivory and a decline in macrophyte abundance are consistent with anec- dotal observations of past fish investigations and contemporary data. The study dem- onstrates the usefulness of applying zooplankton subfossils to detect long-term changes in the trophic structure of brackish lakes in the past. In addition, it draws at- tention to the difficulties of using sediment records to highlight short-term events, such as fish kills, in shallow wind-impacted lakes.

Effects of climate variations on pelagic ocean habitats and their role in structuring forage fish distributions in the Bering Sea

Ecological responses to climate perturbations and minimal sea ice in the northern Bering Sea

Interannual variability of coccolithophore Emiliania huxleyi blooms in response to changes in water column stability in the eastern Bering Sea

A macrodescriptor perspective of ecological attributes for the Bering and Barents Seas

Cetacean distribution and relative abundance on the central–eastern and the southeastern Bering Sea shelf with reference to oceanographic domains

The potential impact of elevated sea surface temperature (SST) and pCO2 on algal community structure and particulate dimethylsulfoniopropionate (DMSPp) concentrations in the southeastern Bering Sea was examined using a shipboard “Ecostat” continuous culture system. The ecostat system was used to mimic the conditions projected to exist in the world's oceans by the end of this century (i.e. elevated pCO2 (750 ppm) and elevated SST (ambient + 4°C). Two experiments were conducted using natural phytoplankton assemblages from the high-nutrient low-chlorophyll (HNLC) central basin and from the middle domain of the southeastern continental shelf. At the HNLC site, the relative abundances of haptophytes and pelagophytes were higher and the relative abundance of diatoms lower under “greenhouse” conditions (i.e. combined 750 ppm CO2 and elevated temperature) than control conditions (380 ppm CO2 and ambient temperature). This shift in algal community structure was accompanied by increases in DMSPp (2–3 fold), DMSPp:Chl a (2–3 fold) and DMSP:PON (2 fold). At the continental shelf site, the changes in the relative abundances of haptophytes, pelagophytes and diatoms under “greenhouse” conditions were similar to those observed at the HNLC site, with 2.5 fold increases in DMSPp, 50–100% increases in DMSPp:Chl a and 1.8 fold increases in DMSP:PON. At both locations, changes in community structure and the DMSPp parameters were largely driven by increasing temperature. The observed changes were also consistent with the phytoplankton-DMS-albedo climate feedback mechanism proposed in the Charlson-Lovelock-Andreae-Warren (CLAW) hypothesis.

Over the past decade the positive trends in the average annual number of fish larvae and in the copepod population dynamics in the coastal area of the Black Sea agree. The increased fish larvae abundance is hypothesized due to improvement of their nutrition associated with the drastic increase in number of introduced invasive cyclopoid copepod Oithona davisae. This assumption is difficult to be verified through fish gut content analysis in absence of methodology allowing prey species identification from their fragmentary residual remnants. Our paper offers an original approach to identification of several common copepod prey using specific distinctive features detected on their chitin fragments from guts of fish larvae and juveniles. To identify specific features of the common species from the coastal areas off Sevastopol (Acartia tonsa, Oithona davisae, Longipedia sp., Cyclopina sp.), alive copepods were isolated from the samples and reared as monospecific cultures in laboratory. Images of alive copepods of each species at successive stages of development and their moulted exoskeletons were compared with the images of chitin remnants found in the fish guts. This technique discloses relatively intact specific morphological features remaining undigested in chitin fragments of prey. These species-specific taxonomic features are suggested to be used for trophic analysis of the Black Sea fishes at early stages of development. Application of proposed method is helpful for assessment of qualitative and quantitative composition of consumed prey and selectivity of fish, especially during the changes in zooplankton community structure affecting significantly survival of fish generations.