Small time scale plankton structure variations at the entrance of a tropical eutrophic bay (Guanabara Bay, Brazil)

Abstract

A B S T R A C TThe dynamics of the plankton compartments at the entrance of Guanabara Bay (SE Brazil) were assessed during a short-term temporal survey to estimate their trophic correlations. Size-fractioned phytoplankton (picoplankton: < 2µm, nanoplankton: 2-20µm and microplankton: > 20µm) biomass and photosynthetic efficiency, composition and abundance of the auto-and heterotrophic nano-and microplankton, and mesozooplankton were evaluated at a fixed station for 3 consecutive days at 3-h intervals, in the surface and bottom (20m) layers. The variability of almost all plankton compartments in the surface layer was directly dependent on temperature, indicating the great influence of the circulation at the entrance of the bay on plankton structure. In the surface layer, the mesozooplankton seems to be sustained by both autotrophic nano-and picoplankton, this last being channeled through the microzooplankton. Near the bottom, both auto-and heterotrophic microplankton are probably supporting the mesozooplankton biomass. Our findings thus suggest that the entrance of Guanabara bay presents a multivorous food web, i.e., a combination of both grazing and microbial trophic pathways. R E S U M OA dinâmica dos vários compartimentos do plâncton foi avaliada durante uma série de curta duração na entrada da baía de Guanabara (SE do Brasil), com o objetivo de estimar suas correlações tróficas. A biomassa e eficiência fotossíntética das três frações do fitoplâncton (picoplâncton: < 2µm, nanoplâncton: 2-20µm e microplâncton: > 20µm), juntamente com a composição e abundância do nano-e microplâncton auto-e heterótrofos e do mesozooplâncton, foram determinadas em uma estação fixa durante 3 dias consecutivos, a intervalos de 3h, nas camadas de superfície e de fundo (20m). A variabilidade de quase todos os compartimentos do plâncton na superfície foi diretamente relacionada à temperatura, indicando forte influência da circulação da entrada da baía na estrutura planctônica. Na camada superficial, o mesozooplâncton parece ser alimentado pelo nano-e picoplâncton autótrofos, esse último sendo sustentado pelo microzooplâncton. Próximo ao fundo, o microplâncton auto-e heterótrofo estão possivelmente sustentando a biomassa mesozooplanctônica. Nossos resultados sugerem, portanto, que na entrada da baía de Guanabara esteja estabelecida uma rede trófica multívora, i.e., uma combinação entre as cadeias microbiana e de pastagem.

A strong CO&lt;sub&gt;2&lt;/sub&gt; sink enhanced by eutrophication in a tropical coastal embayment (Guanabara Bay, Rio de Janeiro, Brazil)

“…In general, highest values were recorded during summer conditions and lower values during winter. This feature has also been observed in other studies Guenther et al, 2012). S3, S4 and S5 experienced the densest phytoplankton blooms, with Chl a reaching maxima on one occasion of 537 µg L −1 in S3, 289 µg L −1 in S4 and 822 µg L −1 in S5.…”

“…Its geomorphological characteristics and rather complex circulation of water masses make it difficult to apply standard approaches to discern sources or sinks from composite plots between salinity and material concentrations (Bourton and Liss, 1976). Furthermore, Guanabara Bay has been considered one of the world's most degraded embayments, characterized by constant eutrophic to hypertrophic conditions and the frequent occurrence of red tides (Rebello et al, 1988;Villac and Tennenbaum, 2010;Guenther et al, 2012). The CO 2 behaviour in Guanabara Bay is different from that in most of documented estuaries worldwide.…”

Spatial and seasonal variation of microphytoplankton community and the correlation with environmental parameters in a hypereutrophic tropical estuary - Maranhão - Brazil

“…According to VALENTIN et al (1999), that is a response to the intense eutrophication process in large and sporadic nutrients pulsing favoring the dominance of larger cells. However, when the photosynthetic efficiencies are compared, the nano/pico phytoplankton are superior and the synthesis is always of large scale (RODRIGUES;CUTRIM, 2010;GUENTHER et al, 2012).…”

Estuary Adjacent to a Megalopolis as Potential Disrupter of Carbon and Nutrient Budgets in the Coastal Ocean

“…Algae blooms have been frequently observed in the outer bay region as well as in the adjacent coastal region. 44 DO and pH are correlated in the linear data fits (C1: DO = -17.98 + 3.15 pH, r = 0.603, p < 0.05; C2: DO = -27.21 + 3.78 pH, r = 0.807, p < 0.05) demonstrating dominance of biochemical process 45 as driver of DO and pH values from surface to bottom waters. Similar slopes but very different intercepts (C1 = -17.9 and C2 = -27.2) also support that in C2 respiration exceeded primary production thereby generating a greater decrease in DO than in pH.…”

“…The significant positive linear correlations between DO and Chl-a (r = 0.635; p < 0.01), of DO and bacteria counting (r = 0.550; p < 0.01), as well as of Chl-a and bacteria counting (r = 0.423; p < 0.01) only in C2 may be taken as an indication of respiration activity (bacteria and other grazing) exceeding primary production in the entire water column including the photic zone. 44 This may occur subsequent to the incidence of an algae bloom. Algae blooms have been frequently observed in the outer bay region as well as in the adjacent coastal region.…”