Can ephemeral proliferations of submerged macrophytes influence zoobenthos and water quality in coastal lagoons?

Abstract

Hydrology is often the main determinant of water chemistry and structure of the aquatic communities in coastal lagoons, driven by the interaction of freshwater load from the catchment and marine intrusions. However, submerged aquatic vegetation (SAV) can have important local effects on both features, even during sporadically and short proliferations. A SAV summer proliferation was observed during 2003 in a coastal lagoon in Uruguay (Laguna de Rocha), increasing macrophyte cover and biomass in the less saline zones. SAV summer proliferations were first observed in summer 2001, with no records prior. The aim of this paper is to describe the ephemeral proliferation of SAV in this shallow brackish lagoon and to analyze its effects on the abiotic environment and on the zoobenthic community. Vegetated and unvegetated zones were sampled in the northern more limnic area (9.1 mS cm -1 ± 4.8) and the southern brackish area (20.9 mS cm -1 ± 5.2). Water and sediment chemistry were analyzed by standard methods and benthos and plants were collected with an Ekman grab. During SAV proliferation, suspended solids were five times lower inside macrophyte patches and water column total phosphorus and nitrogen were three and two times lower, respectively. Zoobenthos abundance and richness were higher in vegetated patches. However, no differences were found between sampling sites in the more brackish southern area and in the North after the SAV proliferation ended. This indicates that SAV can influence water chemistry and benthos structure above a biomass threshold of 100 g DW m -2 . Although hydrology is the driving force regulating communities and water chemistry in these coastal lagoons, our results showed that SAV can also be an important local factor above a certain biomass threshold.

Environmental Variability and Macrophyte Assemblages in Coastal Lagoon Types of Western Greece (Mediterranean Sea)

“…The structure and composition of these four macrophyte assemblages distinguished in the coastal lagoons of Western Greece was determined by the abiotic gradients [1] and the degree of isolation by the sea [7]. Due to the higher variability of abiotic gradients (transparency and salinity) and the hydrological regime in lagoons, diversity is generally lower than in more stable and marine environments [60,61]. The detrended correspondence analysis showed that lagoon type, salinity and nutrient concentrations played relatively important roles on species distribution and succession [62].…”

Migratory benthic fishes may induce regime shifts in a tropical floodplain pond

“…Independent of climatic region, water level fluctuation is an important factor that should be considered in river-floodplain ecosystems (Junk, Bayley & Sparks, 1989;Neiff, 1990;Thomaz, Bini & Bozelli, 2007). Although temperate ecosystems have been more frequently investigated than those at other latitudes, new findings on regime shifts have also been reported for tropical (Loverde-Oliveira et al, 2009) and subtropical lakes (Rodriguéz-Gallego et al, 2010), where the role of fish-macrophyte interactions seems to differ from that in temperate lakes (Meerhoff et al, 2007). Although temperate ecosystems have been more frequently investigated than those at other latitudes, new findings on regime shifts have also been reported for tropical (Loverde-Oliveira et al, 2009) and subtropical lakes (Rodriguéz-Gallego et al, 2010), where the role of fish-macrophyte interactions seems to differ from that in temperate lakes (Meerhoff et al, 2007).…”

Photoalteration of macrophyte-derived chromophoric dissolved organic matter induces growth of single bacterial populations in a coastal lagoon

“…The differences in optical characteristics found between both plants may reflect differences in their chemical composition for these species (Farjalla et al, 2001). Previous studies have shown that sedimentary organic matter in Laguna de Rocha is mainly derived from the macrophyte community (Conde and Sommaruga, 1999) and two of the most abundant plant species in this lagoon are S. californicus and R. maritima (Rodríguez-Gallego et al, 2010). Furthermore, Piccini et al (2009) showed that CDOM photoalteration in Laguna de Rocha stimulates bacterioplankton activity and induces changes in bacterioplankton community composition in few hours, suggesting that photochemical processes are important for the availability of the organic matter derived from macrophytes.…”

“…Mey.) Palla and the widgeongrass Ruppia maritima L. (Rodríguez-Gallego et al, 2010), is a relevant process shaping the heterotrophic bacterial community.…”