The impact of temporal variability in light-climate on time-averaged primary production and a phytoplankton bloom in a well-mixed estuary

A significant increase in the human population on marine coast and steady growth of maritime water transport causes the construction of port infrastructure and the creation of new lands, which affects the ecosystems of coastal waters. Despite the widespread occurrence of such large-scale engineering projects in coastal areas, their impact on various components of aquatic ecosystems, including phytoplankton, is still poorly understood. The aim of the study was to assess the effect of the construction of ports and the alluvium of new lands in the Neva Estuary in 2000s on the productivity of phytoplankton. Digging and dredging of bottom sediments results in one order of magnitude elevation of suspended particulate matter (SM), which mostly consisted of sand and clayed deposits and in significant decrease water transparency, as compared to the average long-term values. Concentrations of total phosphorus in the estuarine waters during the works significantly positively correlated with the concentrations of SM. However, the multiple increase in nutrients was less important for phytoplankton development than expected. Analysis of variance and stepwise multiple regression analyses showed that the main predictor of the primary production of plankton in the periods of construction was water transparency. Gross primary production decreased significantly. In contrast to short-term effects caused by wind-induced events, which often stimulated phytoplankton development, long-term construction works of new port facilities negatively influenced phytoplankton productivity. Apart from pristine conditions when the phosphorus concentration was the main factor limiting the primary production in the estuary, the main limiting factor during long-term engineering projects became water transparency. Taking into account plans for further development of ports in coastal areas around the world, the influence of the large-scale engineering projects on the conditions for the development of phytoplankton may provide a new aspect of long-term regulation of algal blooms and ecosystem functioning in the coastal and estuarine zones.

Section: Primary Production Of Planktonsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Impact of the Construction of New Port Facilities on Primary Production of Plankton in the Neva Estuary (Baltic Sea)

Golubkov

Голубков²

2022

“…The numerical results of suspended sediments indicated that the suspended sediment concentration decreased northeast of the river mouth and increased south of the river mouth after the MEC. The changed suspended sediment concentration regulated the turbidity distribution, which has a significant influence on the phytoplankton growth in the estuarine area (Kromkamp and Peene, 1995;Horemans et al, 2020). Zhu et al (2009) demonstrated that high turbidity restrained the phytoplankton growth at the Changjiang River mouth, and a good correlation between turbidity and phytoplankton biomass can be established through seasonal field observations adjacent to the Changjiang River Estuary.…”

Section: Effect Of the Mega Estuarine Constructions-induced Suspended Sediment Concentration Variationmentioning

confidence: 99%

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

Wang

2022

Massive large-scale engineering projects have been built in river estuaries around the world, but their effects on environments in the surrounding coastal waters were less emphasized compared to those due to the watershed projects. In this study, we used the Changjiang River Estuary as an example to show that a significant consequence can be resulted in such a situation. Through analyzing the harmful algal bloom events data and the chlorophyll satellite data, we investigate the spatiotemporal variations of algal blooms in the estuary and its adjacent water. The results indicate that the location of algal bloom hotspot changed over the period of the estuarine constructions. Furthermore, using a well-validated numerical model, we explored the mechanisms responsible for such an ecosystem regime shift. It was found that after the estuarine constructions were built, the surface chlorophyll maximum was attenuated and part of it migrated landward north of the river mouth but was strengthened south of the river mouth and extended seaward. Alternations of the nutrient concentration distribution and turbidity distribution induced by river plume deviation are responsible for the redistribution of the high chlorophyll concentration area. By contrast, the direct impact of the Three Gorges Dam through changing the runoff and sediments flux, which has been highlighted in numerous studies, was less important than expected. Given the fact that Three Gorges Dam and mega estuarine constructions were built in a similar period, any observed regime shift of hydrodynamic and ecological status outside the estuary should be interpreted with particular caution.

“…Various factors may have contributed to this abrupt change due to the complex physical and biochemical interactions in the PRE (Yin et al, 2000;Huang et al, 2003;Zhang and Li, 2010). Researchers have noticed that changes in the riverine sediment loads might be essential in controlling biological processes by regulating the turbidity distribution, which significantly influenced phytoplankton growth in estuaries (Cloern, 1987;Tian et al, 2009;Horemans et al, 2020).…”

Section: Ecological Symptoms and Potential Influencing Factorsmentioning

confidence: 99%

A comprehensive approach to assessing eutrophication for the Guangdong coastal waters in China

Zhou,

Wang

2024

Eutrophication is a global issue associated with increasing anthropogenic activities. Previous studies have mainly focused on nutrients and phytoplankton biomass in some typical estuaries and bays along the Guangdong coast, while integrated evaluations of eutrophication status based on ecological symptoms is still rare in this area. To better understand the health of the Guangdong coastal waters, two comprehensive methods including the Assessment of Estuarine Trophic Status (ASSETS) and the Northwest Pacific Action Plan Common Procedure (NOWPAP CP) were employed with slight modifications. The study area was divided into eight coastal zones (Z1~Z8) based on multiple criteria including salinity, catchment range, and administrative division. The results of the modified NOWPAP CP method demonstrated a generally increasing trend in the degree and effects of nutrient enrichment along the Guangdong coast in the past 30 years mainly due to the increasing nutrients and chlorophyll a (Chl-a). The results of the modified ASSETS method revealed that the water quality was between moderate and high for most coastal zones during 2015-2018, with the highest score (0.83) in the northern part of the Pearl River Estuary (PRE). However, the ecological symptoms showed inconsistent spatial patterns with the water quality, being high or moderate high in Z2 (including Zhanjiang Harbor and Leizhou Bay), Z4~Z5 (representing the northern and southern parts of the PRE, respectively), and Z6 (containing Mirs Bay and Daya Bay) for severe ecological symptoms, such as high levels of Chl-a, frequent harmful algal blooms (HABs). Moreover, eutrophication in Z4~Z6 may further deteriorate due to the increasing nutrient loads driven by growing economy and population. Synthetically, Z2, Z4~Z6 were graded between poor and bad for the overall eutrophication conditions (OEC), while Z1 (including the western and southern parts of the Leizhou Peninsula) and Z7 (consisting of Honghai Bay and Jieshi Bay) had a good OEC. The application of the modified ASSETS method effectively identified areas of severe eutrophication problems and the prospect of nutrient load along the Guangdong coast. The assessment results revealed the spatiotemporal variations and potential trends in the eutrophication status, providing scientific basis for the coastal management related to nutrient problems.