Changing water quality and thermocline depth along an aquaculture gradient in six tropical crater lakes

Abstract

Understanding how lakes respond to changes in nutrient loading along a productivity gradient can help identify key drivers of aquatic change, thereby allowing appropriate mitigation strategies to be developed. Physical, chemical and biological water column measurements combined with long-term water monitoring data for six closely located crater lakes, in Southeast Asia, were compared to assess the response of lakes along a productivity gradient equating to a transect of increasing aquaculture intensity. Increasing chlorophyll a (phytoplankton biomass) in the upper waters appeared to modify the thermocline depth and light availability causing a shift from a deep chlorophyll maximum at low aquaculture intensity to the emergence of algal dead zones lower in the water column with high aquaculture intensity. High phosphorus loading and light limitation from enhanced algal biomass, associated with high aquaculture intensity, exacerbated nitrogen drawdown, leading to the prevalence of potentially nitrogen-fixing cyanobacteria. Seasonal overturn during the cooler season resulted in low dissolved oxygen concentrations in the epilimnion, potential harmful algal blooms, a reduction in the habitable depth for fish and ultimately increased mortality amongst farmed fish.

Community structure of plankton in Whiteleg Shrimp, Litopenaeus vannamei (Boone, 1931), pond ecosystem

“…Eutrophication conditions in ponds are not good for cultured shrimp. This is because waters that experience eutrophication will result in low levels of dissolved oxygen in ponds (Astuti et al 2022;Briddon et al 2023). Plankton found in whiteleg shrimp ponds from this study can be seen in Figure 4.…”

The methane-oxidizing microbial communities of three maar lakes in tropical monsoon Asia

“…A simultaneous study with Aguilar et al (2023) categorized the mixing patterns of the SMLs with Lakes Palakpakin, Bunot, Mohicap, Sampaloc, and Yambo being warm monomictic while the two deepest lakes Pandin and Calibato were categorized as meromictic. Thermal stratification of the lakes was observed during the SW monsoon from August 2018 and April and May 2022 while the complete mixing of the whole water column of Lake Yambo and the epilimnion of both Lakes Pandin and Calibato happened during the NE monsoon from November to February, which causes CH 4 concentrations to be released from the water column into the atmosphere ( Forster et al, 2007 ; Schubert et al, 2010 ; Mendoza et al, 2019 ; Mendoza-Pascual et al, 2021 ; Briddon et al, 2022 ). Lake Yambo, the deepest of the SML monomictic lakes, was selected as the primary study site to represent warm monomictic-mesotrophic lakes, while Lakes Pandin and Calibato, which are mesotrophic-meromictic and eutrophic-meromictic, respectively, were chosen as study sites to initially assess the diversity of the MOB community during the period of stratification (SW; August 2018) and mixing (NE; February 2019) ( Table 1 ).…”

Environmental significance of kaolinite variability over the last centuries in crater lake sediments from Central Mexico

“…In summer, the intense rainfall increases water turbidity and dilutes nutrients in the stratified upper water column, leading to a reduction in biological productivity (Gomez-Tagle Chavez et al, 2002). Among other meteorological forcings, the impact of wind action on thermal stratification is limited in crater lakes due to their low surface/depth ratio and steep crater walls (Kienel et al, 2009;Briddon et al, 2023).…”