Changes In Zooplankton Community Research Articles

Autumn‐to‐Spring Energetic and Diet Changes among Kokanee from North Idaho Lakes with and without Mysis relicta

AbstractChanges in the Pend Oreille Lake, Idaho, zooplankton community during spring and autumn have been attributed to planktivory by the opossum shrimp Mysis relicta. To examine how the altered zooplankton community affects kokanee Oncorhynchus nerka, we compared seasonal body lipids and feeding patterns of age‐0 and age‐1 individuals from Pend Oreille Lake with those of kokanee from Coeur d'Alene and Spirit lakes, Idaho, which did not contain M. relicta. We also contrasted our feeding pattern analysis with results of a similar study conducted in Pend Oreille Lake before M. relicta introduction. Age‐0 Pend Oreille Lake kokanee showed no evidence of malnourishment, as body lipids and feeding patterns were generally similar among the three lakes. Age‐1 Pend Oreille Lake kokanee had lower body lipids and stomach fullness than age‐1 kokanee in the other lakes, suggesting that zooplankton community changes might affect older kokanee. We saw no evidence of direct starvation mortality in either Pend Oreille Lake year‐class, since body lipids were higher than prior studies have reported for starving individuals. Seasonal kokanee feeding patterns were similar between age‐classes but differed among lakes, Pend Oreille Lake individuals consuming a lower proportion of Daphnia during autumn compared with Coeur d'Alene Lake and Spirit Lake fish. Kokanee fed upon small copepod species during spring in all three lakes. Before M. relicta establishment in Pend Oreille Lake, kokanee in autumn ate a higher proportion of cladocerans, consumed a greater total prey biomass, and had fewer empty stomachs, but spring feeding patterns were more similar to those we observed. Our results show that seasonal changes in zooplankton availability in Pend Oreille Lake have probably changed age‐1 kokanee foraging and energy accumulation patterns, particularly in autumn, although we cannot exclude the possibility that recent changes in predation intensity may also explain our results.

Relationships between frontal structures and zooplankton communities along a cross-shelf transect in the Bay of Biscay (1995 to 2003)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 284:65-75 (2004) - doi:10.3354/meps284065 Relationships between frontal structures and zooplankton communities along a cross-shelf transect in the Bay of Biscay (1995 to 2003) Aitor Albaina*, Xabier Irigoien Marine Research Division, AZTI Foundation, Herrera Kaia Portualde, z/g 20110, Pasaia (Gipuzkoa), Spain *Email: aalbaina@pas.azti.es ABSTRACT: A high-resolution cross-shelf transect in front of the mouth of the Gironde estuary (45.62°N, and from 1.36 to 4.27°W, with 3 nautical miles between stations) is carried out once a year during the spring stratification period. In this study, we analysed the zooplankton samples in 1995, 1997, 1999, 2001 and 2003 in order to elucidate the effects that mesoscale structures exert over the zooplankton community. The Gironde river plume and a shelf-break front due to internal wave generation over the slope are the main frontal structures described along the transect. Their position and magnitude determine zooplankton community changes both qualitatively and quantitatively. Two peaks of zooplankton abundance and distinct zooplankton assemblages were found to be related to the river plume and the frontal structure associated with the shelf-break. However, the distribution of biomass was more homogenous, suggesting that other factors apart from enhancement of primary production related to the location of frontal structures are involved in the determination of the pattern of secondary production along the transect. KEY WORDS: Fronts · Zooplankton · Mesoscale structures · Bay of Biscay · Internal waves · Gironde river plume · Shelf-break Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 284. Online publication date: December 21, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Seasonal Zooplankton Abundance and Size Fluctuations across Spatial Scales in Lake Pend Oreille, ldaho

ABSTRACT We studied seasonal zooplankton community dynamics along spatial scales in Lake Pend Oreille, Idaho in 1997–1998 to determine if zooplankton community changes brought about by establishment of Mysis relicta in the 1970's persist today, and to relate zooplankton length and abundance fluctuations to zooplanktivory. Long-term trends in zooplankton species composition and relative abundance, as well as seasonal patterns of species succession are apparently unchanged since M. relicta establishment. Cladoceran zooplankters became abundant earlier in the spring and remained abundant later into autumn in 1998 than in 1997. Fluctuations in zooplankton lengths and abundance were more pronounced along horizontal gradients extending from littoral to pelagic zones than along vertical gradients extending downward from the surface, and these fluctuations were more pronounced in 1998 than in 1997. Zooplankton length variability along spatial scales occurred most often in late spring/early summer, and in autumn. The trends we observed are consistent with prior speculation that zooplanktivory by M. relicta structures the Lake Pend Oreille zooplankton community, although abiotic factors may also explain our results.

PH 6 as the threshold to use in critical load modeling for zooplankton community change with acidification in lakes of south-central Ontario: accounting for morphometry and geography

Identifying thresholds of biotic community change along stressor gradients may be useful to both ecologists and lake managers; however, there are several weaknesses in the thresholds that have been identified for zooplankton communities along acidity gradients. The thresholds are often based on a single species even though pH sensitivities vary among species. They often measure changes in species occurrences, though abundances may be a more responsive indicator of damage. Their identification may be confounded by spatial and morphometric factors if they are derived from lake surveys. Finally, the thresholds have usually been subjectively identified. Our goal was to establish a threshold in zooplankton community change along an acidity gradient that did not have these four common weaknesses. We used two crustacean zooplankton community metrics: species richness and scores of a correspondence analysis based on species abundances. Spatial and morphometric patterns were detected in the zooplankton community data and then extracted. The relationship between zooplankton and acidity was then modeled using a step function that objectively identified a threshold of community change at pH 6 for lakes in south-central Ontario.

Crustacean zooplankton communities in lakes recovering from acidification

Large reductions in sulphur emissions at the Sudbury, Ont., Canada, smelters in recent decades have resulted in decreased lake acidity, and biological improvements have followed. Lakes in the Sudbury area offer a very unique opportunity to develop our understanding of the processes regulating biological restructuring in aquatic ecosystems recovering from acidification. Here, we examine changes in crustacean zooplankton communities that have accompanied the chemical recovery of Whitepine and Sans Chambre lakes, near Sudbury, over the last two decades. In both these formerly acidic lakes, pH has increased to ~6.0, and some zooplankton community recovery has occurred. However, zooplankton communities have not completely recovered based on multivariate comparisons with the community composition of reference lakes. Although a number of acid-sensitive species have appeared, many did not persist, or did not achieve abundances typical of the reference lakes. This indicates that zooplankton community recovery will most likely depend on biotic and abiotic interactions within these lakes and not on factors affecting species dispersal. Both chemical and biological factors have large influences on biological recovery processes. Assessing biological recovery is very important since the restoration of healthy aquatic communities is a major objective of large-scale sulphur emission control programs.

Changes in the zooplankton community of the British Columbia continental margin, 1985-1999, and their covariation with oceanographic conditions

Changes in the zooplankton community of the British Columbia continental margin, 1985-1999, and their covariation with oceanographic conditions

Spatial and temporal changes in copepod zooplankton communities of Lake Tanganyika

Pelagic Copepoda zooplankton in Lake Tanganyika were sampled over two years at three localities. When the data from both years were pooled, post-naupliar cyclopoids formed 76% of the pelagic post-naupliar Copepoda off Bujumbura, 83% off Kigoma and 62% off Mpulungu. During both sampling years, dry weight biomass of post-naupliar copepod stages decreased at sampling sites in the order Bujumbura > Kigoma > Mpulungu. Cyclopoids off Kigoma showed a clear seasonal pattern with one abundance peak in October/November and another at the end of the wet season in April/May. At other locations, neither cyclopoids nor calanoids showed clear seasonal pattern. Correlation of seasonal biomass was low between the first and second dry seasons, and between the first and second wet seasons in all the sampling localities and in all the zooplankton groups. The yearly mean post-naupliar copepod dry weight biomass was estimated as 3.1 g dw m-2 off Bujumbura, 2.1 g dw m-2 off Kigoma and 1.5 g dw m-2 off Mpulungu.

Top‐down or Bottom‐up Effects by Fish: Issues of Concern in Biomanipulation of Lakes

AbstractA large‐scale biomanipulation trial was carried out on Lake Vesijärvi in Finland during 1989–1993. Following the mass removal of coarse fish the biomass of cyanobacteria collapsed from 1.4 g/m−3 to below 0.4 g/m−3, while total phosphorus concentration declined from 45 μg/L to 30 μg/L. No relevant changes in zooplankton communities were observed. The results suggest that the success of food web manipulation as a tool for lake restoration is not necessarily dependent on the grazing rate of zooplankton. The effects of reduced fish‐mediated internal loading and recycling of nutrients are in many cases stronger than those of reduced planktivory. Alternative stable states of water quality may also exist in lakes not covered by macrophytes, owing to the changes in the behavior of fish stocks. Year‐to‐year variation in the littoral zone may cause large oscillations in lake ecosystems—for example, through the recruitment of fish. In addition, the nutrients translocated by fish from the littoral zone may affect the nutrient dynamics of the pelagial plankton community. In terms of phytoplankton species composition and the ratio of phosphorus to chlorophyll a, the water quality in Lake Vesijärvi has improved in a stepwise fashion within the last 10 years. This is probably due to the fact that the five‐year mass removal of fish in Enonselkä fulfilled the requirement of sustained management of fish stocks in order to maintain nonequilibrial conditions between alternate stable states. The prediction of the water quality development is obscured, however, by spatial and temporal within‐lake variation, which sets high requirements for sampling programs.

Primary and secondary effects of methabenzthiazuron on plankton communities in aquatic outdoor microcosms

The primary and secondary effects of methabenzthiazuron on plankton were studied in outdoor microcosms (6 m3) for five months. Macrophytes, phytoplankton, zooplankton and the emergence of insects were examined. The herbicide was added to nine of the twelve mesocosms in concentrations ranging from 10 to 3371 μg a.i. l−1 in a single application. The other three ponds were used as untreated controls. Phytoplankton population dynamics fluctuated depending on light intensity, temperature, nutrients, competition and herbicide concentrations. Primary production was temporarily inhibited at test concentrations from 89 to 3371 μg l−1. Cryptophyta (Phytoflagellata) showed also a recovery at the higher concentrations during the study period. Other primary producers did not recover at these concentrations, as expected from the disappearance curve of the active ingredient at these concentrations. This was also indicated by structural indices such as the diversity, eveness and similarity index. The lower concentrations evoked no or only short-term, weak responses. Chemical water parameters were strongly influenced by the absence of macrophytes (Elodea canadensis) at the high application rates, which also caused significant changes in zooplankton communities. No effects were observed on macro-invertebrates and benthic organisms. In conclusion, noticeable effects were detected only at concentrations clearly above the effect threshold known from standard laboratory tests with aquatic primary producers.

The macrobenthos of Lake Ontario during 1964 to 1966, and subsequent changes in the deepwater community

From January 1964 through January 1966, Dr. F.P. Ide and colleagues at the University of Toronto Great Lakes Institute (GLI) collected benthic macroinvertebrates from up to 63 stations during each of 16 cruises on Lake Ontario. This intensive survey was conducted at a time of rapidly increasing anthropogenic impact. Total invertebrate abundance decreased with increasing depth; this distribution was bimodal on the northern side of the lake, with peaks at ca. 35 and 80 m. Oligochaeta were more abundant along the southern than on the northern side of the lake, except in Humber Bay. The amphipodDiporeia was rarely collected at most stations near the mouth of the Niagara River. Chironomidae were most abundant in the Kingston Basin but were common throughout the lake at depths less than 50 m. Sphaeriidae were confined to water <100 m deep and were most abundant along the southern shore. When compared with the results of subsequent surveys of the deepwater zone, the GLI data provide evidence of two major shifts in the abundance of benthic animals. Numbers of Oligochaeta decreased by about 40% during 1965 and remained at the lower levels through 1990. The abundance ofDiporeia changed little from 1964 through 1977, but increased sharply between 1977 and 1981. These shifts do not appear to reflect implementation of controls on the discharge of phosphorus, or direct predation by fish. Changes in fish and zooplankton communities and inputs of toxic contaminants seem equally likely to be responsible for the shifts in the deepwater benthic community. We have proposed several predictions which could test the relative importance of biotic interactions or chemical stressors.

Zooplankton community changes in Lake Kinneret (Israel) during 1969?1985

Long-term records (1969–1985) of zooplankton density in Lake Kinneret indicated significant reduction of biomass (Copepods, Cladocera, Rotifera) and production (Copepods, Cladocera). Nauplius and adult copepod densities decreased but those of copepodites did not change. Mesocyclops was suppressed more than the smaller Thermocyclops and males of both genera became more abundant relative to the larger females. Ratios of ‘small/large’ Cladocera densities became higher. Numbers of total cladocerans were stable, and therefore reduction of Cladocera grazing capacity is assumed. The abundant Keratella spp. were reduced. It is likely that intensification of fish visual-attack-predation pressure shifted the size-class structure towards smaller adult copepods and cladocerans. Reduction of Keratella spp. and copepod nauplii was probably affected by increasing pressure of fish filter-feeders. Data on fish food consumption, feeding behaviour and fisheries management suggested their direct impact on long-term changes of zooplankton in Lake Kinneret.

Whole‐lake experiments: The annual record of fossil pigments and zooplankton

The annual record of fossil pigments and zooplankton was compared with detailed contemporaneous records from two manipulated lakes from 1940 to 1986. Annually resolved sedimentary records accurately monitored known changes inplankton communities, identified periods of trophic change, and proved a powerful tool for examining long‐term, complex interactions. Both Paul and Peter Lakes underwent the same three complete changes in their fish assemblages (trout, cyprinid, bass), and Peter Lake received repeated inputs of lime. Alterations in fish community composition produced long‐lived changes in zooplankton communities that cascaded to the microbial level of the food web. Liming, in concert with trophic changes, caused distinctive phytoplankton dynamics in Peter Lake.Paleolimnological data recorded all major plankton dynamics known from coeval limnological data. Specifically, the sediment record showed transitions in cladoceran size structure and species composition, changes in water clarity resulting from both food web and chemical manipulations that affected vertical zonation of primary producers, and changes in absolute abundance of all algal divisions except dinoflagellates. Undegraded Chl a indicated deep blooms and, in conjunction with Chl c, fucoxanthin and β‐carotene, indicated metalimnetic chrysophytes. Transient (2–3 yr) nonselective increases in sedimentation corresponded with increases in grazing rates. Isorenieratene indicated overlap of photic and anoxic zones, revealing changes in transparency and conditions for pigment preservation.

Changes in the zooplankton community after lime treatment of an acidified lake

(1985). Changes in the zooplankton community after lime treatment of an acidified lake. SIL Proceedings, 1922-2010: Vol. 22, No. 5, pp. 3008-3013.

Prey selection by the copepod Diacyclops thomasi

1. Adult females of the predaceous copepod, Diacyclops thomasi, consistently selected for the soft-bodied rotifers Synchaeta pectinata, Polyarthra major and P. remata when presented various combinations of 8 rotifer species and 2 crustacean species as prey. Diacyclops did not select for other small, soft-bodied rotifers such as P. vulgaris and Ascomorpha ecaudis and, for loricate species such as Keratella cochlearis, K. crassa and for large soft-bodied adult Asplanchna priodonta. The small cladocerans, Bosmina longirostris and Chydorus sphaericus also were resistant to predation by this copepod. 2. Increased hunger in Diacyclops increased the clearance rates on both vulnerable and Diacyclops-resistant prey but did not greatly increase mortality of resistant prey relative to vulnerable prey. Sated Diacyclops preferred small, vulnerable prey like P. major over larger-bodied Synchaeta. This effect may be attributed to limited gut space when food is abundant. 3. When Diacyclops was presented different relative proportions of Keratella and Synchaeta at a constant total prey density (500 prey/L), it selected Synchaeta over Keratella in all trial proportions. However, Diacyclops selected more strongly for Keratella (but at a much lower clearance rate than for Synchaeta) when the relative abundance of this predator-resistant species was greatest. These results support optimal foraging in this predator. 4. Predator-prey interactions of the kind reported in this study can help identify important food web pathways and can be used to interpret predator-mediated changes in zooplankton communities in mature.