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

Abstract

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.

The Effect of Glacier Recession on Benthic and Pelagic Communities: Case Study in Herve Cove, Antarctica

“…The moraine in Herve Cove, at a depth of 2-3 m, separates the lagoon from the Ezcurra Inlet and can serve as a physical barrier for many organisms and their larvae, but also protects the bottom communities from destructive impact of icebergs. Ice cover in winter and glacial fresh water discharge in summer might affect inflow of pelagic larvae, decreasing biodiversity of the lagoon and increasing differences in species composition between different lagoons in the same area [35]. The second moraine in the middle of Herve Cove, occurring at depths of approximately 6-7 m, has probably less impact on the benthic distribution, as no differences between benthic communities on both sides of that moraine were observed.…”

“…The inner part of Potter Cove in Maxwell Bay is less than 50 m depth, whereas the outer part is deeper than 100 m, with a shallower sill separating them at a depth of <30m [28]. The morphological shape of cove might be an important factor influencing benthic colonization [35,36]. Transverse moraines are significant barriers [35] preventing homogenization of the communities from outside and inside the cove.…”

“…The morphological shape of cove might be an important factor influencing benthic colonization [35,36]. Transverse moraines are significant barriers [35] preventing homogenization of the communities from outside and inside the cove. The moraine in Herve Cove, at a depth of 2-3 m, separates the lagoon from the Ezcurra Inlet and can serve as a physical barrier for many organisms and their larvae, but also protects the bottom communities from destructive impact of icebergs.…”

Intermittently Closed/Open Lakes and Lagoons: Their global distribution and boundary conditions

“…A C C E P T E D M A N U S C R I P T which has been most widely applied internationally (Roy et al, 2001;Schallenberg et al, 2010;Astel et al, 2016;Netto and Fonseca, 2017).…”

“Geo-archives of a Coastal Lacustrine Eco-system”: Lake Bafa (Mediterranean Sea)

“…The marine and terrestrial geological settings influence each other in the coastal areas [1,2]. The Aegean Sea and its onshore areas have raised a substantial interest of the geologists and geomorphologists, since this region is under a north-south tectonic extension, with the formation of hosts and grabens and occurrence of high seismic activity [3].…”