Regime shifts in coastal lagoons: Evidence from free-living marine nematodes
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Data
2017
Tipo de documento
Artigo de Periodico
Título da Revista
ISSN da Revista
Título de Volume
Área do conhecimento
Ciências Biológicas
Modalidade de acesso
Acesso aberto
Editora
Autores
Netto, Sérgio Antonio
Fonseca, Gustavo
Orientador
Coorientador
Resumo
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 largescale
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.
Palavras-chave
Coastal lagoon