Eutrophication in the Neva Estuary (Baltic Sea): response to temperature and precipitation patterns

Abstract

Estuaries provide valuable ecosystem services but are threatened by eutrophication caused by increasing nutrient concentrations and climatic factors. We tested the hypothesis that cool and rainy weather in midsummer has a stronger stimulatory effect on indicators of eutrophication in the Neva Estuary than warm weather. The analysis showed that the concentration of total phosphorus in the estuary was positively correlated with the amount of precipitation and the number of rainy days in the region. Significant positive relationships were found between precipitation in midsummer and chlorophyll concentrations and plankton primary production in the upper part of the estuary. Chlorophyll concentrations and plankton primary production were higher in years with a rainy and cool July than in years with warm and dry July. Such conditions could negate existing measures to improve water quality in the Neva Estuary, meaning that greater effort will be needed.

Phytoplankton Biomass Dynamics in Tropical Coastal Waters of Jakarta Bay, Indonesia in the Period between 2001 and 2019

“…This temporal increase in phytoplankton biomass was observed in all parts of the bay, with higher levels in 2019 relative to 2001. Mean phytoplankton biomass of this study is comparable to those of the Wadden Sea spring phytoplankton biomass of around 15 µg L −1 [22], Southern German Baltic Sea levels between 22 and 120 µg L −1 [27], and Neva Estuary Baltic Sea values ranging from 6.4 to 33.2 µg L −1 [3]. These values are higher than those for oligotrophic waters of the Eastern Adriatic Sea, which ranged from 2.79 to 4.73 µg L −1 [28], and the tropical Porong Estuary in Indonesia, which ranged from 2.51 to 4.75 µg L −1 [29].…”

“…In all, 15 stations were sampled, covering river mouths (stations at the Angke, Priok, and Marunda Rivers) and the inner (stations 10, 11, 12), middle (stations 2,5,8,3,6,9), and outer parts of the bay (stations 1, 4, and 7). To cover a spatial gradient of riverine input, the gradient of salinity was used to select the sampling sites, ranging from low values at the river mouths and inner part of the bay to high values in the middle and outer parts of the bay [10].…”

“…The increased levels of organic matter and nutrients affect phytoplankton development. However, phytoplankton growth is governed not only by nutrients but also by other factors such as underwater light and physical hydrodynamics [2][3][4][5]. The classic approach to investigating the responses of the phytoplankton community to the two main resources on which it depends (nutrients and light) involves determining which acts as the limiting factor.…”

Stable C and N Isotope Composition of Suspended Particulate Organic Matter in the Neva Estuary: The Role of Abiotic Factors, Productivity, and Phytoplankton Taxonomic Composition

“…Dense reeds of 300-600 m width belt only its shallow coastal zone. A more detailed description of the estuary was given in previous publications [8,29]. [8,28].…”

“…As a result, the primary productivity and biomass of planktonic autotrophic organisms in the estuary are among the highest in the Baltic Sea [8,28]. Recently, eutrophication has been increasing due to unfavorable weather conditions leading to an increase in the production of autochthonous organic matter in the estuary, which is not completely mineralized in the estuary waters and is carried further into the central part of the Gulf of Finland [29]. The phytoplankton of the estuary includes marine and freshwater species, the composition of which differs depending on environmental factors [30].…”