Eurytemora Americana Research Articles

Decadal change in zooplankton seasonal succession in the Bahia Blanca estuary, Argentina, following introduction of two zooplankton species

Seasonal zooplankton succession (mainly of the mesozooplankton) in the inner zone of Bahia Blanca estuary during the period 1990-1991 was compared to that from the period 1979-1980 in order to detect changes having taken place in 10 years. Taxonomic composition, zooplankton abundance, species occurrence and temperature-salinity conditions were studied within the two annual cycles. This estuarine ecosystem has been deeply affected by a population increase and by the rapid growth of industrial activity and maritime traffic over the last two decades. Several changes in the zooplankton assemblage composition and structure were detected, probably due to temperature- salinity gradient patterns, which showed discernible differences. Dominance, during winter-spring, of two new invading species, namely, the cirriped Balanus glandula and the copepod Eurytemora americana, causing a decrease in the autochthonous key copepod Acartia tonsa, was one of the principal features of the period 1990-1991. Seasonal changes in diversity and species richness, as well as differences in the multivariate general pattern of the zooplankton community structure with a consequent decrease in the community stability during the second period, were also observed.

Morphometric variables and individual volume of Eurytemora americana and Acartia tonsa females (Copepoda, Calanoida) from the Bahía Blanca estuary, Argentina

Eurytemora americana and Acartia tonsa are the two most important copepods from the Bahia Blanca estuary plankton. For this study, 30 females were selected from recently preserved samples. Prosome length (PL), width (PW) and height (PH), urosome length (UL) and width (UW) measured in each female and subsequently the following ratios PL/PW, PL/PH, PW/PH and PL/UL were determined. Individual volumes for E. americana and A. tonsa females were estimated following the morphometric method in order to obtain individual biomass values. Regression tests were conducted for both species between individual volume and prosome length or width as independent variables, fitting data to a power model. Regression lines were compared through covariance analysis and single pair comparisons in order to evaluate the temporal behavior of the relationships. PL/UL was the best ratio for separating one species from the other. Average individual volume and std. error estimated for E. americana and A. tonsa were 0.0749 (±0.0097) mm3 and 0.0399 (±0.0049) mm3, respectively. Strong differences between both copepods morphometric variable and rate values were observed. A size and volume decrease was detected associated with higher temperatures and less phytoplankton available for food. According to R2 values of regression lines prosome width and prosome length were good volume predictors on different dates for E. americana, however, prosome width was the best predictor on the majority of dates for A. tonsa. Differences in slopes and mean variances found between regression lines demonstrated seasonal variability. General regression equations between volume and PL or PW for each species could be derived.

<i>Eurytemora americana</i> Williams, 1906, not <i>Eurytemora affinis</i> (Poppe, 1880), inhabits the Bahía Blanca estuary, Argentina

SUMMARY: The aim of this report is to clarify the taxonomical identity of the species of Eurytemora (Copepoda, Calanoida) present in the Bahia Blanca estuary, Argentina. Observations of taxonomical details were performed and the results led us to conclude that this species is Eurytemora americana Williams, 1906 and not Eurytemora affinis (Poppe, 1880), as previously identified. E. americana is a recent invader in this estuary and could have been accidentally introduced with ballast water of ships.

Population and Production Ecology of Zooplankton in Ogac Lake, a Landlocked Fiord on Baffin Island

Collections were analysed from the three basins of the lake in 1957, and from the middle basin of the lake and a fertilized polyethylene column in 1962. The abundant copepod, Pseudocalanus minutus,...

The Planktonic Copepods (Calanoida, Cyclopoida, Monstrilloida) of Ungava Bay, with Special Reference to the Biology of Pseudocalanus minutus and Calanus finmarchicus

Collections of planktonic copepods of Ungava Bay and central Hudson Strait were made during late June, July and August of 1947, 1949 and 1950. The following 22 species have been identified: Calanus finmarchicus, C. hyperboreus, C. helgolandicus, Pseudocalanus minutus, Microcalanus pygmaeus, Gaidius tenuispinus, Aetideopsis rostrata, Pareuchaeta norvegica, P. glacialis, Eurytemora americana, Metridia longa, Pleuromamma robusta, Heterorhabdus norvegicus, Acartia longiremis, A. bifilosa, Oithona similis, Oncaea borealis, Cyclopina gracilis, C. schneideri, Monstrilla dubia, M. helgolandica and M. canadensis. The last 5 species have not previously been recorded from the western North Atlantic. Males of Cyclopina Schneideri are described for the first time. The two most abundant species, Calanus finmarchicus and Pseudocalanus minutus, have one generation a year. A small part of the population of Pseudocalanus minutus breeds a second time in the autumn. The next most common species, Acartia longiremis and Oithona similis, probably breed and spawn in July. The population dynamics of all the species are discussed.