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A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L−1) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L−1). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H’ = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H’ = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status.

The aquaculture industry requires good water quality for its successful operation but produces wastes that can cause environmental deterioration and pose high risks to the sector. Adequate waste treatment and recycling are necessary to make aquaculture a sustainable and profitable industry and contribute to the circular economy. Polluted water sources, excess feeding, overstocking, use of antibiotics/chemicals and harmful algal blooms are major causes of water quality deterioration and low production in aquaculture systems. Discharges of untreated wastes would have serious impacts on the receiving water bodies, and eventually on the aquaculture industry itself. Possible solutions include technological innovations in environmentally friendly production systems, use of efficient processes in water quality management and improved legislation and governance. Environmentally feasible aquaculture production technologies such as recycling aquaculture system, integrated multi-trophic aquaculture and aquaponics including features of waste recycling are viable options in aquaculture schemes. Best aquaculture practices integrating advanced water quality treatment processes and technologies, supported by automation and sensors, modeling and artificial intelligence-internet of things are necessary for a sustainable aquaculture environment, production and stable value chain. In general, low-cost technologies for aquaculture waste treatment and environmental impact reduction through good governance are crucial for achieving sustainability in the aquaculture industry and natural environmental management.

This review investigates the performance and the feasibility of the integration of an algal reactor in recirculating aquaculture systems (RAS). The number of studies related to this topic is limited, despite the apparent benefit of algae that can assimilate part of the inorganic waste in RAS. We identified two major challenges related to algal integration in RAS: first, the practical feasibility for improving nitrogen removal performance by algae in RAS; second, the economic feasibility of integrating an algal reactor in RAS. The main factors that determine high algal nitrogen removal rates are light and hydraulic retention time (HRT). Besides these factors, nitrogen-loading rates and RAS configuration could be important to ensure algal performance in nitrogen removal. Since nitrogen removal rate by algae is determined by HRT, this will affect the size (area or volume) of the algal reactor due to the time required for nutrient uptake by algae and large surface area needed to capture enough light. Constraints related to design, space, light capture, and reactor management could incur additional cost for aquaculture production. However, the increased purification of RAS wastewater could reduce the cost of water discharge in places where this is subject to levees. We believe that an improved understanding of how to manage the algal reactor and technological advancement of culturing algae, such as improved algal reactor design and low-cost artificial light, will increase the practical and economic feasibility of algal integration in RAS, thus improving the potential of mass cultivation of algae in RAS.

Groupers are dispersed worldwide in the tropical and subtropical waters. They are prized in the live reef fish trade, making them candidates with high market value and consumer demand. In the Asian-Pacific region, the brown-marbled grouper (Epinephelus fuscoguttatus) is widely adapted as an aquaculture species. However, health management remains a major concern in the stressful intensive culture process. The present review discusses techniques and current knowledge in the cultivation of E. fuscoguttatus towards healthy fish growth focusing on aspects of immunity, feed, and husbandry. Understanding how the fish immune system responds during infections provides insights into the intricate ways fish resist pathogens. This information is helpful when developing vaccination strategies or immunostimulant compounds to strengthen fish immunity. Feeds that are formulated according to the needs of the fish ensure optimal growth and using suitable alternative ingredients may lower production cost without compromising fish health. Good husbandry practices contribute to a favourable environment for the fish to grow, while interspecific hybridization may be a convenient approach to generate hardier species. Nevertheless, it has been noted that research in E. fuscoguttatus is relatively scarce in contrast to the closely-related orange-spotted grouper (E. coioides), which is used in the present article as a reference. Ultimately, the identified gaps in knowledge between the two species warrant species-specific research in E. fuscoguttatus to promote fish health and ensure continued success in aquaculture. Keywords: Epinephelus fuscoguttatus, Epinephelus coioides, Health, Immunity, Feed, Husbandry

The freezing–thawing method had been reported to be the best phycobiliprotein extraction technique. However, optimum parameters of this extraction method for Arthrospira sp. (one of the major phycobiliprotein sources) still remained unclear. Hence, this study aimed to optimize the freezing–thawing parameters of phycobiliprotein extraction in Arthrospira sp. (UPMC-A0087). The optimization of the freezing–thawing method was conducted using different solvents, biomass/solvent ratios, temperatures, time intervals and freezing–thawing cycles. The extracted phycobiliproteins were quantified using a spectrophotometric assay. Double distilled water (pH 7) with a 0.50% w/v biomass/solvent ratio was the most efficient solvent in extracting high concentrations and purity of phycobiliproteins from Arthrospira sp. In addition, the combination of freezing at −80 °C (2 h) and thawing at 25 °C (24 h) appeared to be the optimum temperature and extraction time to obtain the highest amount of phycobiliproteins. A minimum of one cycle of freezing and thawing was sufficient for extracting high concentrations of phycobiliproteins. The findings from this study could reduce the cost and labor needed for extracting high quality phycobiliproteins. It also allowed the harvesting of large amounts of valuable phycobiliproteins.

The responses of two species of microalgae, Chlorella sorokiniana and Chlorella zofingiensis, were compared regarding their morphological and biochemical properties under photoautotrophic and mixotrophic conditions. These microalgae were cultured under both conditions, and their crude ethanolic extracts were examined for their pigment and total phenolic contents. In addition, the microalgae’s antioxidant activities were determined using a DPPH radical scavenging assay and a ferric reducing antioxidant power (FRAP) assay. Both strains showed increases in cell size due to the accumulation of lipid bodies and other cell contents, especially carotenoids, under the mixotrophic condition. Notably, reductions in phenolic and chlorophyll contents were observed to be associated with lower antioxidant activity. C. zofingiensis compared with C. sorokiniana, demonstrated higher antioxidant activity and carotenoid content. This study showed that different species of microalgae responded differently to varying conditions by producing different types of metabolites, as evidenced by the production of higher levels of phenolic compounds under the photoautotrophic condition and the production of the same levels of carotenoids under both photoautotrophic and mixotrophic conditions.

Recent limnological investigations conducted on the large lakes of Indonesia provide valuable physical and ecological data for future environmental and developmental programmes, yet few studies have focused on zooplankton taxonomy. Here we describe Eucyclops troposperatus Alekseev et Yusoff n. sp. from a pond in Sumatra, and Mesocyclops jakartensis Alekseev n. sp. from a city pond in Jakarta, Java. In the pelagic zone of the lakes of Sulawesi we found only few copepod species. For the endemic cyclopoid Tropocyclops matanoensis Defaye, 2007, we propose a new subgenus, Defayeicyclops n. subg., and provide more data on the morphology as well as scanning electron microscopy and confocal laser scanning images of Tropocyclops (Defayeicyclops) matanoensis. Two other cyclopoid species were possibly introduced to Sulawesi: Mesocyclops aequatorialis similis Van de Velde, 1984 from Africa and Thermocyclops crassus (Fischer, 1853) from Eurasia. A new subspecies, Phyllodiaptomus praedictus sulawesensis Alekseev et Vaillant n. ssp. (Calanoida, Diaptomidae), is described from the plankton of lake Tondano, North Sulawesi, Indonesia. The new subspecies resembles P. blanci (de Guerne et Richard, 1896) and P. wellekensae Dumont et Reddy, 1992. Phyllodiaptomus praedictus sulawesensis appears to be endemic to Sulawesi island. The form matanensis formerly treated as a subspecies of Eodiaptomus wolterecki Brehm, 1933 is here elevated to species rank, E. matanensis Brehm, 1933. A preliminary list of the copepod species found in Sulawesi and other large islands of Indonesia now includes more than 60 species. An updated key to the Southeast Asian species of the genus Eucyclops is provided.