A shallow lake in an agricultural landscape – water quality, nutrient loads, future management

Abstract

Qualitative analyses of nitrogen and phosphorus loads reaching the lake ecosystem provide a basis for pollution control, which is of paramount importance in shallow lakes due to the rapid turn-over of matter and energy. The studies of both external and internal loading were conducted in Lake Łeknenskie, a very shallow, through-flow lake situated in Western Poland. Strong eutrophication is manifested in rich rush vegetation and a lack of submerged macrophytes as well as nitrogen and phosphorus concentrations (max 13.04 mg N dm−3 and 0.32 mg P dm−3, respectively). Constant domination of cyanobacteria in the phytoplankton community was noted in almost all seasons with a 98% share in summer, resulting in 20 cm water transparency and 223 μg dm−3 of chlorophyll-a. The zooplankton community was dominated by rotifers. The main source of nutrients was the River Nielba. Spatial external nutrient loading was 1.93 g P m−2 yr−1 and 77.55 g N m−2 yr−1. An even higher load of phosphorus was released from the bottom sediments, 2.18 g P m−2 yr−1. A comprehensive action plan is required, aiming at the reduction of both external and internal nutrient loading. A series of solutions regarding local environmental conditions should be applied in the lake catchment, including biogeochemical barriers, denitrification walls, artificial retention basins or wetlands, but most of all – improvement in the functioning of the wastewater treatment plant. Restoration is possible, however, protection measures reducing external loading should be undertaken prior to phosphorus inactivation in the water column and in the bottom sediments, supported by biological methods e.g. biomanipulation.

Are the existing guidelines sufficient for the assessment of bathing water quality? The example of Polish lakes

“…The presented studies have shown that small water bodies with bathing waters were significantly less frequently monitored in all the referred monitoring programs. The reason for this in Poland is the law regulation requiring that only lakes larger than 50 ha might be monitored in the national SMS system coordinated by CIEP (Ciecierska and Kolada 2014 ; Dondajewska et al 2019 ). Thus, small lakes, ponds, and other water reservoirs used for bathing did not have a chance to be investigated in detail, unlike the larger lakes, in accordance with the WFD in EU countries.…”

Microalgal diversity assessment of Laguna Lake (Philippines) tributaries using Next-Generation Sequencing for water quality

“…Hill, 1991 has been identified as contributing to red tide events in many countries (Yoo et al 2017). The C. curvata has been associated with high levels of dissolved total phosphorus and dissolved total nitrogen (Xia et al 2014;Dondajewska et al 2019).…”

Influence of land use and occupation on water quality and on the diatom community of reservoirs in northeast Brazil

“…Eutrophication is one of the well-described impacts of the present time, almost always associated with the increase in cyanobacteria biomass and a drastic reduction of submerged macrophytes (Dondajewska et al, 2019), besides the simplification of the trophic structure, loss of biodiversity and species extinction (Dubey and Dutta, 2020). Therefore, an increase of nutrients is directly associated with the primary production increase and, consequently excessive growth of algae (Ballah et al, 2019).…”