Assessment of Water Quality Based on Trophic Status and Nutrients-Chlorophyll Empirical Models of Different Elevation Reservoirs

Water quality degradation is one of the most pressing environmental challenges in reservoirs around the world and makes the trophic status assessment of reservoirs essential for their restoration and sustainable use. The main aims of this study were to determine the spatial variations in water quality and trophic state of 204 South Korean reservoirs at different altitude levels. The results demonstrated mean total phosphorus (TP), chlorophyll-a (CHL-a), total suspended solids (TSS), organic matter indicators (chemical oxygen demand: COD; total organic carbon: TOC), water temperature (WT), and electrical conductivity (EC) remain consistently higher in the very lowland reservoirs (VLLR) than those in other altitudes, due to sedimentary or alluvial watersheds. The average TP and CHL-a levels in VLLR crossed the limit of the eutrophic water, symptomizing a moderate risk of cyanobacterial blooms. Empirical models were developed to identify critical variables controlling algal biomass and water clarity in reservoirs. The empirical analyses of all reservoir categories illustrated TP as a better predictor of CHL-a (R2 = 0.44, p < 0.01) than TN (R2 = 0.02, p < 0.05) as well as showed strong P-limitation based on TN:TP ratios. The algal productivity of VLLR (R2 = 0.61, p < 0.01) was limited by phosphorus, while highland reservoirs (HLR) were phosphorus (R2 = 0.23, p < 0.03) and light-limited (R2 = 0.31, p < 0.01). However, TSS showed a highly significant influence on water clarity compared to TP and algal CHL-a in all reservoirs. TP and TSS explained 47% and 34% of the variance in non-algal turbidity (NAT) in HLR. In contrast, the TP and TSS variances were 18% and 29% in midland reservoirs (MLR) and 32% and 20% in LLR. The trophic state index (TSI) of selected reservoirs varied between mesotrophic to eutrophic states as per TSI (TP), TSI (CHL-a), and TSI (SD). Mean TSI (CHL-a) indicated all reservoirs as eutrophic. Trophic state index deviation (TSID) assessment also complemented the phosphorus limitation characterized by the blue-green algae (BGA) domination in all reservoirs. Overall, reservoirs at varying altitudes reflect the multiplying impacts of anthropogenic factors on water quality, which can provide valuable insights into reservoir water quality management.

Water quality for triathlon and open water swimming competitions in Brazilian freshwaters

In high-performance competitive activities, there can be intense and prolonged exposure to water during swimming components of the competition. Therefore, water quality assessments with reference to standards are desirable to ensure athletes’ health. We evaluated whether the official criteria established for primary contact recreation in Brazilian freshwaters (CONAMA Directive 274/2000), and an integrated index of bathing conditions in Brazil (ICB), are consistent with the water quality standards stipulated by the International Triathlon Union (ITU). The water quality of Lake of Ingleses, an important venue for triathlon and open water swimming near Belo Horizonte, Minas Gerais, Brazil, was assessed between 2003 and 2019. Results for E. coli, cyanobacteria density, and pH were favorable for contact recreation and competitions at the lake. Of the variables considered, only turbidity, used as a proxy indicator of visual water clarity, was unsuitable during part of the monitoring period. The ICB agreed with the ITU standards for Very Good and Excellent quality classes and is recommended as a tool for screening sites considered for competitions in Brazilian freshwaters. However, the Brazilian national criteria for contact recreation only present standards for E. coli and pH, which is insufficient coverage of attributes affecting primary contact suitability of water in high-performance sports activities.

Marine Sites and the Drivers of Wellbeing: Ecosystem vs. Anthropic Services

Coastal sites offer a range of services that contribute to human wellbeing. While some of the services are entirely human-made (e.g., parasol and sunbed rental), others are produced thanks to the contribution of marine ecosystems (e.g., water clarity). The purpose of this paper is to investigate the preferences of a sample of beachgoers for these two categories of services that policymakers have to balance when designing management strategies for coastal sites. We consider a marine site in the north of Italy that partially falls within the boundaries of a protected area but that is characterized by a medium-to-high level of anthropization. The results of a discrete choice experiment show that in the current state of things, the ecosystem services proposed for the sample have, on average, a higher marginal utility, suggesting that actions increasing those services have a larger effect on well-being.

Acoustic Approach to Determining Seabed Substrates Distribution at Mandi Darah Island, Sabah

Marine ecosystems and natural habitat play the important role of the Earth’s life support system. They significantly contribute to economies and food safety and help preserve ecological processes. However, the devastation of the marine ecosystem in Malaysia due to the human factor and climate change is quite alarming. Therefore, spatial marine information, especially on the distribution of seabed substrates and habitat mapping, are of utmost importance for marine ecosystem management and conservation. Traditionally, seabed substrate and habitat mapping were classified based on direct observation techniques such as photography, video, sampling, coring and scuba diving. These techniques are often limited due to water clarity and weather conditions and only suitable for smaller scale surveys. In this study, we employed an acoustic approach using the RoxAnn Acoustic Ground Discrimination System (AGDS) with a high-frequency single-beam echo sounder to examine the distribution of seabed substrate at the Mandi Darah Island, Sabah. The acoustic signals recorded by AGDS are translated into hardness and roughness indices which are then used to identify the unique characteristics of the recorded seabed types. The analysis has shown that fifteen types of substrates, ranging from silt to rough/some seagrass, have been identified and classified. The findings demonstrated that the acoustic method was a better alternative for seabed substrate determination than the conventional direct observation techniques in terms of cost and time spent, especially in large scale surveys. The seabed substrate dataset from this study could be used as baseline information for the better management and conservation of the marine ecosystem.

MORTALITY OF BLACK-BAND MYLEUS Myloplus Schomburgkii DUE TO POOR WATER QUALITY ASSOCIATED WITH OVERPOPULATION OF DUCKWEEDS IN A CULTURE POND IN THE PERUVIAN AMAZONIA

Ponds covered with duckweeds release nutrients rapidly, causing problems of eutrophication of the water which can reduce water clarity and quality, creating a hypoxic or anoxic ‘dead zone' lacking sufficient oxygen to support most organisms. In the present study, the sudden mortality of black-band myleus Myloplus schomburgkii Jardine, 1841 drove the investigate of factors that caused the death of the specimens registered in a fish pond in the Peruvian Amazon. After the tallying of dead fish, it was revealed that sixty individuals (75% of the total population) of M. schomburgkii had died. The taxonomic identification of the aquatic plant revealed the presence of “duckweeds” locally named in Peru as “lenteja de agua” Lemna minor distributed throughout the pond. Physical and chemical water parameters revealed low levels of oxygen, acid water, and high levels of nitrate and phosphate. Since duckweeds cannot be completely eliminated from waters that are conducive to its growth and require periodic harvesting to prevent matting, proper management strategies therefore become critical to guarantee good quality of water in the pond and avoid black-band myleus deaths due to imbalances in physical and chemical parameters.

Can Plants Be Engineers?

When we think of engineers, we think of making a machine, like a car. Are there engineers for ecosystems? When an organism can make big changes to its environment, we call it an ecosystem engineer. In aquatic ecosystems like the San Francisco Estuary, underwater plants can be important ecosystem engineers because they can change water flow and water clarity. In the Estuary, a plant called Brazilian waterweed, which was introduced by humans, is one of the most important ecosystem engineers. With its leaves and stems, this plant traps tiny particles floating in the water, making the water clearer. Clearer water has made it easier for more plants to grow and these changes helped some non-native fish species to increase in number, while some native species declined. Introduction of Brazilian waterweed has led to an entirely different ecosystem, which has also affected how people use and take care of the Estuary.