Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts

Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships.Estuários são ecossistemas costeiros que sustentam uma ampla variedade de serviços ambientais para a humanidade. Estuários abrigam muitos ambientes bentônicos com características específicas e seriamente ameaçados globalmente. Manguezais, marismas e planícies de maré são amplamente impactados por poluentes domésticos e industriais, por atividades comerciais que levam à perda de habitat e pela sobrepesca. Os diversos impactos locais, associados a mudanças regionais e globais na hidromorfologia estuarina e potenciais efeitos de mudanças climáticas, colocam sérias ameaças a ecossistemas estuarinos. A rede Bentos foi criada para estudar o efeito de mudanças no clima em ecossistemas bentônicos costeiros brasileiros. Este trabalho faz parte dos esforços iniciais do Grupo de Trabalho Estuários em rever o conhecimento sobre comunidades bentônicas estuarinas no Brasil. Aqui apresentamos uma breve revisão crítica sobre os trabalhos realizados objetivando o estudo, em nível de comunidades, do bentos estuarino e processos ecológicos associados. A partir do cenário atual, realizamos recomendações de estudo para responder questões científicas sobre efeitos de mudanças climáticas em comunidades bentônicas estuarinas, e enfatizamos a necessidade de bases de dados contínuas e de longa duração e o estabelecimento de parcerias internacionais com foco específico nos estuários brasileiros

Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts

Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships

Regime shifts in coastal lagoons: Evidence from free-living marine nematodes

<div><p>We test the validity of using the regime shift theory to account for differences in environmental state of coastal lagoons as a response to variation in connectivity with the sea, using free-living nematodes as a surrogate. The study is based on sediment samples from the inner and outer portions of 15 coastal lagoons (5 open to the sea, 5 intermittently open/closed, and 5 permanently closed lakes) along the southern coast of Brazil. Environmental data suggested that there are two contrasting environmental conditions, with coastal lakes being significantly different from open and intermittent lagoons. Marine nematode assemblages corroborate these two mutually exclusive alternative stable states (open vs. closed systems), but assemblages from the intermittently open/closed lagoons showed a gradual change in species composition between both systems independently of the environmental conditions. The gradient in the structural connectivity among lagoons and the sea, due to their regime shifts, changes the movement of resources and consumers and the internal physico-chemical gradients, directly affecting regional species diversity. Whereas openness to the sea increased similarity in nematode assemblage composition among connected lagoons, isolation increased dissimilarity among closed lagoons. Our results from a large-scale sampling program indicated that as lagoons lose connectivity with the sea, shifting the environmental state, local processes within individual intermittently open/closed lagoons and particularly within coastal lakes become increasingly more important in structuring these communities. The main implication of these findings is that depending on the local stable state we may end up with alternative regional patterns of biodiversity.</p></div

Summary characteristics of nematode assemblages from coastal lagoons.

<p>Summary characteristics of nematode assemblages from coastal lagoons.</p

Distance-based RDA ordination relating environmental variables to the nematode composition.

<p>GS- grains size; TOC- total organic content; closed (dark blue circle), intermittently open/closed (light blue circle) and open (open circle).</p

Map of the coast of Santa Catarina showing the location of the sampled lagoons: Closed (black circle), intermittently open/closed (gray circle) and open (open circle).

<p>Map of the coast of Santa Catarina showing the location of the sampled lagoons: Closed (black circle), intermittently open/closed (gray circle) and open (open circle).</p

Nematode variation in genera composition (total mean β-diversity), contribution of replacement and richness differences (gray dots) and within in inner outer portions of lagoons (columns).

<p>Different letters indicate significant differences (p<0.05) among lagoon types.</p