Long-term annual and monthly changes in mysids and caridean decapods in a macrotidal estuarine environment in relation to climate change and pollution

© 2018 Elsevier B.V. A 26-year time series of monthly samples from the water intake of a power station has been used to analyse the trends exhibited by number of species, total abundance, and composition of the mysids and caridean decapods in the inner Bristol Channel. During this period, annual water temperatures, salinities and the North Atlantic Oscillation Index (NAOI) in winter did not change significantly, whereas annual NAOI declined. Annual mean monthly values for the number of species and total abundance both increased over the 26 years, but these changes were not correlated with any of the measured physico-chemical/climatic factors. As previous studies demonstrated that, during a similar period, metal concentrations in the Severn Estuary and Bristol Channel (into which that estuary discharges) declined and water quality increased, it is proposed that the above changes are due to an improved environment. The fauna was dominated by the mysids Mesopodopsis slabberi and Schistomysis spiritus, which collectively contributed 94% to total abundance. Both species, which were represented by juveniles, males, non-brooding females and brooding females, underwent statistically-indistinguishable patterns of change in abundance over the 26 years. When analysis was based on the abundances of the various species, the overall species composition differed significantly among years and changed serially with year. When abundances were converted to percentage compositions, this pattern of seriation broke down, demonstrating that changes in abundance and not percentage composition were responsible for the seriation. As with the number and abundance of species, changes in composition over the 26 years were not related to any of the physico-chemical/climatic factors tested. Species composition changed monthly in a pronounced cyclical manner throughout the year, due to statistically different time-staggered changes in the abundance of each species. This cyclicity was related most strongly to salinity

Zooplankton community structure in a highly turbid environment (Charente estuary, France): Spatio-temporal patterns and environmental control

Zooplankton assemblages were studied from January 2007 to January 2008 along the salinity gradient of the Charente estuary (France). A Lagrangian survey was performed monthly at five sampling stations defined by salinity (freshwater, 0.5, 5, 15 and 25) in order to collect zooplankton and measure the main environmental parameters (concentrations of suspended particulate matter, particulate organic carbon, chlorophyll a and phaeopigments). A combination of multivariate cluster analysis, species indicator index and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages with environmental drivers. The estuary was divided into three different zones by means of environmental parameters while four zooplankton assemblages were identified along the salinity gradient. The Charente estuary appeared as one of the most turbid systems in Europe, with suspended particulate matter (SPM) concentration reaching 3.5 g l-1 in the Maximum Turbidity Zone (MTZ). Algal heterotrophy and microphytobenthos resuspension from the wide mudflats could be responsible for the relatively high chlorophyll a concentrations measured within this MTZ. Salinity and SPM affected significantly the spatial distribution of zooplankton species while temperature and river flow seemed to control their temporal variations. From a zooplanktonic viewpoint, the highly turbid Charente estuary seemed to match an "ecotone-ecocline" model: the succession of species assemblages along the salinity gradient matched the concept of ecocline while the MTZ, which is a stressful narrow area, could be considered as an ecotone. Although such ecoclinal characteristics seemed to be a general feature of estuarine biocenoses, the ecotone could be more system-specific and biological compartment-specific. © 2010 Elsevier Ltd. All rights reserved

20 | Gauda – Girrei

Publié avec le concours du Centre national du livre (CNL) et sur recommandation du Conseil international de la philosophie et des sciences humaines (UNESCO). Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn : 978-2-7449-0028-0

24 | Ida – Issamadanen

Publié avec le concours du Centre national du livre (CNL) et sur recommandation du Conseil international de la philosophie et des sciences humaines (UNESCO). Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn : 978-2-7449-0249-9

14 | Conseil – Danse

Publié avec le concours du Centre national du livre (CNL) et sur recommandation du Conseil international de la philosophie et des sciences humaines (UNESCO). Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn : 978-2-85744-741-2

14 | Conseil – Danse

Publié avec le concours du Centre national du livre (CNL) et sur recommandation du Conseil international de la philosophie et des sciences humaines (UNESCO). Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn : 978-2-85744-741-2