Temporal patterns of phytoplankton assemblages, size spectra and diversity during the wane of aPhaeocystis globosaspring bloom in hydrologically contrasted coastal waters

Abstract

The space-time dynamic of phytoplankton diversity and succession was investigated during the wane of a Phaeocystis globosa spring bloom in four distinct hydrological sub-systems of the eastern English Channel. Nutrients, chlorophyll-a concentrations, and phytoplankton composition, standing stocks, size spectra and diversity were monitored during three key periods in 2003: late spring, early summer and summer. Two consecutive diatom assemblages were observed, respectively dominated by: (i) small colonial species (,100 mm; Melosira sp., Diploneis sp. and Navicula transitans) in April; and (ii) large fine-walled cells (.200 mm; Guinardia striata and Rhizosolenia imbricata) in May and July. This shift in diatom composition appeared to be related to the potentially limitating silicic acid in early summer. Specific phytoplankton assemblages identified in distinct water masses have evolved from a mature/senescent community towards a relatively homogeneous aestival structure of dominant species that might have been triggered by the wane of the P. globosa bloom. Our results also identified a strong heterogeneity in the distribution of secondary species between distinct water masses during the summer period, suggesting that the magnitude of the observed patterns was intrinsically related to the hydrological properties prevailing in each sub-system. The identification of distinct temporal patterns in phytoplankton species diversity and succession following the wane of a spring bloom at relatively small spatial scales (i.e. ,10 km) is discussed in the framework of P. globosa blooms in particular and phytoplankton blooms in general and is suggested to have potentially strong consequences on food web dynamics and the carbon cycle in coastal ecosystems.

Respuesta del microfitoplancton a la adicion de nitrato y acido silicico en fiordos de la Patagonia chilena

“…por sobre las otras especies debido a que de las mencionadas anteriormente, es aquella con menor razón S/V. Por lo tanto, posee una constante de saturación media (Ks) para el Si(OH)4 más baja y necesita menores concentraciones de ácido silícico para desarrollarse de manera óptima (Reynolds, 2006;Alves-de-Souza et al, 2008;Schapira et al, 2008).…”

The use of mussels for mitigating the noxious effect of phytoplankton spring blooms on farmed fish

“…As the domoic acid producing Pseudo-nitzschia genus has been previously observed in the study area (Antajan et al, 2013;Schapira et al, 2008), total domoic acid (i.e. dissolved and particulate) in seawater was quantified in both tanks using ASP ELISA kits (Biosense Laboratories, Bergen, Norway).…”

“…P. globosa degradation in favour of spring to summer diatom assemblages (Pseudo-nitzschia sp., Guinardia sp. ; Rousseau et al, 2002;Schapira et al, 2008;Seuront et al, 2006) is highlighted by high pheopigment contribution to total pigments (i.e. 78-93% of chlorophyll a + pheopigments).…”

Parasitic Eukaryotes in a Meso-Eutrophic Coastal System with Marked Phaeocystis globosa Blooms

“…The recurrent massive proliferation of the Haptophyte Phaeocystis globosa is associated to the surplus of nitrogen and silicate limitation atlate winter (Peperzak et al, 1998). Abundant populations of colonial diatoms and dinoflagellate grazers are observed before and after the P. globosa bloom (e.g., Schapira et al, 2008;Grattepanche et al, 2011a,b and references therein). A winter-summer succession study of planktonic protists, by means of 18S rRNA gene high-throughput sequencing approach, suggested that the previously well-established food web concept in the EEC based on predator-prey (e.g., grazer-phytoplankton) interactions is "just a part of the ecological picture" and in fact several organisms using a variety of previously "overlooked" strategies, such as parasitism and saprotrophy, were abundant members of the planktonic community .…”