Response of phytoplankton to organic enrichment and shrimp activity in tropical aquaculture ponds: a mesocosm study

Abstract

We conducted a mesocosm study to investigate the combined effect of organic enrichment and sediment resuspension by shrimp on phytoplankton communities in shrimp aquaculture ponds. Hence, the factorial design included two factors, i.e., (i) shrimp density with a concomitant increase of feed input resulting in organic enrichment and (ii) with/without access of shrimp to the sediments. Increasing feed input in the system raised the eutrophication state of the environment characterized by an increase in phytoplankton biomass. Bioturbation enhanced (i) mineralization of organic matter via the microbial loop, resulting in faster nutrient recycling, (ii) an increase of primary production, and (iii) buffering capacity against eutrophication consequences. The phytoplankton community showed both large temporal variations of its taxonomic composition and resilience to treatments. A shift in species dominance from Diatoms + Dinoflagellates to green algae was observed in all treatments and coincided with meteorological and N pool changes. Results suggested that algal production was primarily limited by phosphorus and light at low (i.e. low feeding) and high (i.e. high feeding) eutrophication states, respectively. Growth rate appeared as an important factor of dominance in this highly dynamic ecosystem. Consequences for water column management are discussed.

Temporal variability of benthic-pelagic coupling in shallow enclosed environment: A case study with eutrophying shrimp ponds

“…Those results are consistent with our earlier study Lemonnier et al (2017), which showed an increase in the organic mineralization rate in the water column as a result of sediment resuspension by bioturbation.…”

Dynamics and succession of plankton communities with changing nutrient levels in tropical culture ponds of whiteleg shrimp

“…As also reported by Yusoff et al (2002) and Lemonnier et al (2017), phytoplankton blooms occur in response to increased amounts of nutrients from the metabolic wastes of shrimp. Smith (1983) suggested that in tropical areas where the temperature is high and light is abundant, phytoplankton blooming could be due to the rapidly changing nutrient concentration and nitrogen:phosphorus ratios.…”

“…The high nitrate concentration, which ranged from 4−105 µM in the ponds, is favorable for the growth of diatoms (Malone 1980). The dominance of particular algal groups in aquaculture ponds is affected by abiotic and biotic factors such as salinity (Chien 1992), light (Burford 1997), pond-flushing (Tseng et al 1991), organic enrichment (Lemonnier et al 2017) and nutrient concentrations and their ratios (Boyd 1995, Paerl & Tucker 1995. Diatoms require a wide variety of inorganic nutrients for growth, but the most important are nitrogen and phosphorus (Dawes 1981).…”

“…A positive effect on water quality and productive shrimp performance during the co-culture of 3 species of microalgae and shrimp in a zero-water exchange system was recently demonstrated by Ge et al (2016). Species succession is often ob served in shrimp ponds, starting with some beneficial flagellate and diatom species, followed by unfavourable noxious dinoflagellates after a month of culture (Yusoff et al 2002, Lemonnier et al 2016, Lemonnier et al 2017.…”

“…Phytoplankton stabilize the whole pond ecosystem by minimizing wide fluctuations in water quality and preventing build-up of waste nutrients to toxic levels, thereby ensuring better shrimp growth and yields (Ziemann et al 1992, Burford 1997, Lemonnier et al 2017. A positive effect on water quality and productive shrimp performance during the co-culture of 3 species of microalgae and shrimp in a zero-water exchange system was recently demonstrated by Ge et al (2016).…”