Eutrophication Of Coastal Waters Research Articles

An overview of harmful algal blooms and eutrophication in Jakarta Bay, Indonesia

Algal blooms have been occurring in Jakarta Bay for twenty years. However, recently the occurrence of algal blooms, their harmful effects, and their duration have been intensified. Algal blooms have devastated the marine environment, caused fish mortality, and been detrimental to local tourism, local fishing, and other industries along the coast. It comes to speculation that the increase of anthropogenic activity from surrounding areas is taking a toll on the environment. So, this research aimed to study the recent rise of algal blooms in Jakarta Bay and the possible anthropogenic links, mainly through cultural eutrophication, to the increasing occurrence of red tides and their impact. Observation has been conducted to study the dynamic of algal blooms concerning eutrophication and the existing seasons. Collecting samples were performed using a canonical plankton net from 2008 until 2015. The results showed that the abundance of phytoplankton ranged from 40.90 x 106 up to 1699.10 x 106 cells.m−3. The highest quantity of cells was observed in May 2010 between rainy to dry seasons. There is evidence that the reported increase in frequency and magnitude of algal bloom events in Jakarta Bay is linked to cultural eutrophication. The recent exponential growth of the city may be a contributing factor in the increasing intensity of algal blooms. The cultural eutrophication of coastal waters increased, leading to the intensity and frequency of algal bloom.

Carbon Transfer Processes of Food Web and Trophic Pathways in a Tropical Eutrophic Seagrass Meadow

Seagrass meadows provide important habitats and rich organic carbon sources for consumers at different trophic levels but are threatened by accelerating eutrophication in coastal waters. Nevertheless, at present, carbon transfer processes throughout the food web and trophic pathways in eutrophic seagrass meadows are still poorly known. To resolve this issue, carbon sources of different trophic communities in a eutrophic tropical seagrass meadow [Xincun (XC) bay, South China Sea] under eutrophication were examined in summer and winter using dual stable isotopes. The δ13C value of omnivores and carnivores overlapped more with that of herbivores and planktivores/filter feeders, which mainly overlapped with that of epiphytes in summer and macroalgae in winter. Meanwhile, epiphytes and macroalgae exhibited high biomass and corresponding highest contribution to herbivores, omnivores, and carnivores in summer and winter, respectively. These results suggest that the grazing food chain was the main trophic pathway in this eutrophic seagrass meadow, and that the transfer of carbon flow in the grazing food chain was mainly dominated by the proliferating epiphytes or macroalgae carbon. In contrast, the contribution of seagrass to detritivores in both seasons was higher than that of other food sources. Our findings suggest that in eutrophic tropical seagrass meadows, the proliferation of epiphytes or macroalgae induced by high nutrient loading, as well as their seasonal changes, has a greater impact on the transfer of carbon in the grazing food chain than that in the detritus food chain, and the seagrass fueled the food web mainly through the detritus food chain.

An Improved Eutrophication Assessment Algorithm of Estuaries and Coastal Waters in Liaodong Bay

Eutrophication is considered to be a significant threat to estuaries and coastal waters. Various localized studies on the world’s oceans have recognized and confirmed that the Forel-Ule Color Index (FUI) or optical measurements are proportional to several water quality variables based on the relatively clear Chl-a-based waters. However, the application potential of FUI in the turbid estuary with complex optics has not been explored. In this study, we selected the coastal waters in the northern Liaodong Bay as the study area, using the field hyperspectral reflectances (Rrs) collected in 2018 to correct the hue angle and verify the Sentinel-2 images algorithm of FUI by in situ FUI in 2019–2020. The results show that there is a good agreement (R2 = 0.81, RMSE = 1.32, MAPE = 1.25%). Trophic Level Index (TLI) was used to evaluate the eutrophication status. The relationship between the in situ FUI and TLI collected in 2018 was discussed based on the difference in the dominant components of waters, while a number of non-algae suspended solids in the estuaries and coastal waters led to the overestimation of eutrophication based on FUI. The R(560)–R(704) (when FUI is between 11 and 15) and R(665)/R(704) (when FUI is between 19 and 21) was employed to distinguish total suspended matter (TSM)-dominated systems in the FUI-based eutrophication assessment. Based on the analysis, a new approach to assessing the eutrophication of coastal waters in Liaodong Bay was developed, which proved to have good accuracy by the field data in 2019 and 2020 (accuracy is 79%). Finally, we used Sentinel-2 images from Google Earth from 2019 to 2020 and locally processed data from 2018 to analyze the FUI spatial distribution and spatial and temporal statistics of the trophic status in the northern Liaodong Bay. The results show that the northern Liaodong Bay always presented the distribution characteristics of high inshore and low outside, high in the southeast and low in the northwest. The nutrient status is the worst in spring and summer.

Response of Aquatic Organisms Communities to Global Climate Changes and Anthropogenic Impact: Evidence from Listvennichny Bay of Lake Baikal

Simple SummaryLake Baikal is ranked first among the world’s lakes in terms of freshwater reserves (23,000 km3). It is a UNESCO World Heritage Site, and its biota is represented by unique fauna and flora, with endemics accounting for more than 60%. What is happening in the Baikal ecosystem in recent decades due to global climate change and anthropogenic impacts? In this paper, we studied this issue on the example of one of the few open bays on the western shore of Lake Baikal, as well as of some remote areas. It has been found that the plankton composition is dominated by thermophilic species; the role of endemic species in the formation of total biomass is decreasing, which confirms the ecosystem’s response to climate warming. As a result of human activity, filamentous algae bloom suppresses endemic algae species and reduces mollusk proportion. The coastal zone of Lake Baikal is taking on the features of common shallow freshwater lakes due to the predominance of cosmopolitan and widespread Palearctic species. It is necessary to monitor the Baikal ecosystem in the changing climate and to strengthen control over human activities on the shores of the lake.Recent studies have revealed how the freshwater biota of Lake Baikal responds to climate change and anthropogenic impacts. We studied phyto- and zooplankton, as well as phyto- and zoobenthos, in the open coastal waters of the southern basin of the lake and of Listvennichny Bay. A total of 180 aquatic organism taxa were recorded. The response of the Baikal ecosystem to climate change can be traced by changes in the species composition of planktonic communities of the lake’s open coasts in summer. The key species were thermophilic the Anabaena lemmermannii P. Richt. (Fij = +0.7) blue-green algae, the Asplanchna priodonta Gosse (Fij = +0.6) rotifers in 2016, the Rhodomonas pusilla (Bachm.) Javorn. (Fij = +0.5) cold-loving algae, and the Cyclops kolensis Lilljeborg (Fij = +0.9) copepods in the past century. The proportion of Chlorophyta decreased from 63% to 17%; the Cyanophyta increased from 3% to 11% in the total biomass of phytoplankton; and the proportion of Cladocera and Rotifera increased to 26% and 11% in the biomass of zooplankton, respectively. Human activity makes an additional contribution to the eutrophication of coastal waters. The Dinobryon species, the cosmopolitan Asterionella formosa Hass. and Fragilaria radians Kütz., dominated phytoplankton, and filamentous algae, Spirogyra, dominated at the bottom in the area with anthropogenic impact. The trophic level was higher than at the unaffected background site: the saprobity index varied from 1.45 to 2.17; the ratio of eutrophic species to oligotrophic species ranged from 1:2 to 3:1, and the ratio of mesosaprobiont biomass to endemics biomass ranged from 2:1 to 7:1. Currently, the boundaries of eutrophication zones of shallow waters in Lake Baikal are expanding, and its coastal zone has acquired features typical of freshwater bodies of the eutrophic type.

Elevated pCO2 Impedes Succession of Phytoplankton Community From Diatoms to Dinoflagellates Along With Increased Abundance of Viruses and Bacteria

Eutrophic coastal regions are highly productive and greatly influenced by human activities. Primary production supporting the coastal ecosystems is supposed to be affected by progressive ocean acidification driven by increasing CO2 emissions. In order to investigate the effects of high pCO2 (HC) on eutrophic plankton community structure and ecological functions, we employed 9 mesocosms and carried out an experiment under ambient (∼410 ppmv) and future high (1000 ppmv) atmospheric pCO2 conditions, using in situ plankton community in Wuyuan Bay, East China Sea. Our results showed that HC along with natural seawater temperature rise significantly boosted biomass of diatoms with decreased abundance of dinoflagellates in the late stage of the experiment, demonstrating that HC repressed the succession from diatoms to dinoflagellates, a phenomenon observed during algal blooms in the East China Sea. HC did not significantly influence the primary production or biogenic silica contents of the phytoplankton assemblages. However, the HC treatments increased the abundance of viruses and heterotrophic bacteria, reflecting a refueling of nutrients for phytoplankton growth from virus-mediated cell lysis and bacterial degradation of organic matters. Conclusively, our results suggest that increasing CO2 concentrations can modulate plankton structure including the succession of phytoplankton community and the abundance of viruses and bacteria in eutrophic coastal waters, which may lead to altered biogeochemical cycles of carbon and nutrients.

Valorization of the green seaweed Ulva rigida for production of fungal biomass protein using a hypercellulolytic terrestrial fungus

The green macroalgae biomass accumulated in eutrophicated coastal waters has negative ecological and economic impacts. Green macroalgae have an interesting nutritional profile that can be exploited for production of feeds. Bioconversion of green seaweed by microbial fermentation allows the production of microbial biomass protein. This research aimed to study the saccharification and fermentation of green macroalgae biomass by a cellulolytic fungus to provide a product with a nutritional added-value. For this purpose, green seaweed Ulva rigida was directly saccharified and fermented in batch using the filamentous fungus Trichoderma reesei Rut-C30. The fermentation product obtained from the growth of T. reesei Rut-C30 on Ulva rigida as the sole carbon source in 72 h was called fungal biomass protein (FBP) from fermented Ulva rigida. FBP from fermented Ulva rigida contained all essential amino acids and compared favorably with the FAO guideline profiles. Besides, the content of limiting amino acid methionine of FBP from Ulva rigida increased 4-folds compared to the raw alga (from 0.65% to 3% of the total protein content) and was similar to the methionine levels of ovalbumin protein. The in vitro digestibility of FBP from fermented Ulva rigida increased from 71% to 94% compared to the raw alga, and was higher than that of leguminous seeds and similar to that of soybean meal. The results of our work demonstrate that Ulva rigida can be saccharified and fermented in a single step by a terrestrial fungus in 72 h under submerged fermentation to provide high-quality proteins suitable to produce feeds.

Development of a sub-seasonal cyanobacteria prediction model by leveraging local and global scale predictors

In recent decades, cultural eutrophication of coastal waters and inland lakes around the world has contributed to a rapid expansion of potentially toxic cyanobacteria, threatening aquatic and human systems. For many locations, a complex array of physical, chemical, and biological variables leads to significant inter-annual variability of cyanobacteria biomass, modulated by local and large-scale climate phenomena. Currently, however, minimal information regarding expected summertime cyanobacteria biomass conditions is available prior to the season, limiting proactive management and preparedness strategies for lake and beach safety. To address this, sub-seasonal (two-month) cyanobacteria biomass prediction models are developed, drawing on pre-season predictors including stream discharge, phosphorus loads, a floating algae index, and large-scale sea-surface temperature regions, with an application to Lake Mendota in Wisconsin. A two-phase statistical modeling approach is adopted to reflect identified asymmetric relationships between predictors (drivers of inter-annual variability) and cyanobacteria biomass levels. The model illustrates promising performance overall, with particular skill in predicting above normal cyanobacteria biomass conditions which are of primary importance to lake and beach managers.

Coastal eutrophication in China: Trend, sources, and ecological effects

Eutrophication in coastal waters caused by excess nutrient inputs has occurred widely on a global scale. Due to the rapid economic development over the last four decades, most of the Chinese coastal waters have experienced a eutrophic process. Major observed trends of coastal eutrophication include two periods, a slow development from the 1970s to 1990s and a fast development after 2000, with major contributions of increased nitrogen (N) and phosphorus (P) from river inputs, atmospheric deposition, and submarine groundwater discharge (SGD). Nutrient composition and stoichiometry have been significantly changed, including increased ammonium, bioavailable organic N and P, and asymmetric ratios between N, P and silicate (Si). Most of these changes were related to the rapid increases in population density, fertilizer application, sewage discharge, aquaculture and fossil fuel combustion, and have resulted in distinctly increased harmful algal blooms. Coastal eutrophication combined with the effects of climate change is projected to continually grow in coming decades. Targeted research is therefore needed on nitrogen reduction and control, potential adaptation strategies and the consequences for ecosystems and economic sustainability.

Nitrogen removal through oyster cultivation: Integration with artificial fertilization makes it more efficient

The use of bivalve aquaculture to mitigate eutrophication in coastal waters has been proposed for years. As nitrogen overenrichment is usually accompanied by comparative shortages in silicate and phosphate, bivalve cultivation integrated with artificial fertilization may exhibit better nitrogen removal performance than bivalve cultivation alone. During a 15-day mesocosm experiment in a nitrogen-eutrophicated, phosphate-limited coastal pond, the nitrogen fixation in oyster tissue under rice husk ash (RHA)11RHA, rice husk ash. fertilized conditions was 10 times higher than that in the oyster-only treatments with the same density. Meanwhile, the concentrations of dissolved inorganic nitrogen (DIN) and particulate nitrogen (PN) in the combined oyster-fertilization treatments decreased by 87.0% and 57.2%, respectively. Compared with the RHA fertilization treatments, the net DIN consumption was significantly lower and decreased with the oyster density in the oyster-only treatments. The dissolved N/Si ratio decreased from 1.44 to 1.01 and 0.93 in the control and fertilization treatments, respectively, whereas in the oyster-only treatments, it increased to 3.74 at low density and 29.15 at high density. Our results indicate that oyster cultivation can stimulate the regeneration of nitrogen in dissolved forms and intensify relative silicate shortages. The integration of RHA fertilization mediated silicate shortage and helped maintain a balanced dissolved N/Si ratio. Moreover, the combined oyster-RHA fertilization enhanced nitrogen removal efficiency and biomass accumulation and increased the feasibility of oyster cultivation as a cost-effective nitrogen reduction measure.

In situ characterization of benthic fluxes and denitrification efficiency in a newly re-established mussel farm

Mussel farming has been proposed as a mechanism to mitigate eutrophication in coastal waters. However, localizing the intensive filtration of organic matter by mussels can cause a concomitant enrichment of organic matter in sediments below farms, which may influence biogeochemical processes and fates of nutrients in the system. In the context of mitigating eutrophication, it is important to quantify sedimentary changes induced at early life stages of mussel farms. Accordingly, this study investigated how a newly re-established mussel farm affected sedimentation rates, sediment characteristics, sediment-water solute fluxes and nitrate (NO3−) reduction rates (measured in situ) during the first year of production. Sedimentation rates were enhanced at the farm relative to a reference station, and both organic and inorganic carbon accumulated in the sediment with time. Increased organic matter input likely drove the slightly elevated sedimentary effluxes of ammonium (NH4+) and dissolved inorganic phosphorus (DIP) in the farm. Denitrification was the main NO3− reduction process, however, there was a relative increase in the remobilization of bioavailable nitrogen underneath the farm as dissimilatory nitrate reduction to ammonium (DNRA) rates were enhanced by >200% and the denitrification efficiency was 49% lower compared to the reference station. The sedimentary methane (CH4) release tended to be higher at the farm, but fluxes were not significantly different from reference conditions. Low sedimentary pigment concentrations indicated a reduced presence of benthic microalgae at the farm, which likely influenced sediment-water solute fluxes. Over the production cycle, the release of dissolved inorganic nitrogen (DIN) and DIP underneath the farm were respectively 426% and 510% relative to reference conditions. Impacts of the mussel farm were thus measurable already during the first year of establishment. These immediate changes to the sediment biogeochemistry, as well as long-term effects, should be considered when estimating the environmental impact of mussel aquaculture.

Eutrophication Driven by Aquaculture Fish Farms Controls Phytoplankton and Dinoflagellate Cyst Abundance in the Southern Coastal Waters of Korea

We examined the dynamics of dinoflagellate cyst and phytoplankton assemblages in eutrophic coastal waters of Korea, adjacent to fish and shellfish farms. Water temperature showed seasonality, whereas salinity and pH remained relatively consistent. Dissolved inorganic nutrient levels were higher in September and at the inner stations, where aquaculture fish farms are located than those in May and at the outer stations. Canonical correspondence analysis and artificial neural network analysis revealed multiple environmental factors that affect the distribution of phytoplankton and dinoflagellate cysts. Diatoms dominated in the phytoplankton assemblages, while the protoperidinioid group dominated in the dinoflagellate cyst assemblages. Cyst abundance was higher at the outer stations than at the inner stations due to transport by fast currents, and phytoplankton abundance was positively correlated with cyst abundance. An increase in diatom abundance led to an increase in heterotrophic/mixotrophic cyst abundance, indicating that excessive uneaten food and urinary waste from the fish farms caused eutrophication in the study region and fast growth of diatoms, thereby contributing to the growth of heterotrophic/mixotrophic dinoflagellates and consequently, high abundance of heterotrophic/mixotrophic dinoflagellate cysts.

Greenhouse gas emissions (CO2 and CH4) and inorganic carbon behavior in an urban highly polluted tropical coastal lagoon (SE, Brazil)

Increasing eutrophication of coastal waters generates disturbances in greenhouse gas (GHG) concentrations and emissions to the atmosphere that are still poorly documented, particularly in the tropics. Here, we investigated the concentrations and diffusive fluxes of carbon dioxide (CO2) and methane (CH4) in the urban-dominated Jacarepagua Lagoon Complex (JLC) in Southeastern Brazil. This lagoonal complex receives highly polluted freshwater and shows frequent occurrences of anoxia and hypoxia and dense phytoplankton blooms. Between 2017 and 2018, four spatial surveys were performed (dry and wet conditions), with sampling in the river waters that drain the urban watershed and in the lagoon waters with increasing salinities. Strong oxygen depletion was found in the rivers, associated with extremely high values of partial pressure of CO2 (pCO2; up to 20,417 ppmv) and CH4 concentrations (up to 288,572 nmol L-1). These high GHG concentrations are attributed to organic matter degradation from untreated domestic effluents mediated by aerobic and anaerobic processes, with concomitant production of total alkalinity (TA) and dissolved inorganic carbon (DIC). In the lagoon, GHG concentrations decreased mainly due to dilution with seawater and degassing. In addition, the phytoplankton growth and CH4 oxidation apparently consumed some CO2 and CH4, respectively. TA concentrations showed a marked minimum at salinity of ~20 compared to the two freshwater and marine end members, indicating processes of re-oxidation of inorganic reduced species from the low-salinity region, such as ammonia, iron, and/or sulfides. Diffusive emissions of gases from the entire lagoon ranged from 22 to 48 mmol C m-2 d-1 for CO2 and from 2.2 to 16.5 mmol C m-2 d-1 for CH4. This later value is among the highest documented in coastal waters. In terms of global warming potential (GWP) and CO2 equivalent emissions (CO2-eq), the diffusive emissions of CH4 were higher than those of CO2. These results highlight that highly polluted coastal ecosystems are hotspots of GHG emissions to the atmosphere, which may become increasingly significant in future global carbon budgets.

Spatial and temporal variations of nutrients and chlorophyll a in the Indus River and its deltaic creeks and coastal waters (Northwest Indian Ocean, Pakistan)

Nutrient dynamics play an important role in mangroves and adjacent coastal ecosystems. This paper discusses the spatiotemporal variation of physicochemical factors in two monsoons and intermonsoons and their influence on chlorophyll a and the dissolved inorganic nutrient concentrations in selected creeks. The present study focused on dense mangrove cover creeks (Waddi Khuddi (WK) and Dabbo (DC)), sparse mangrove cover creek (Hajamro (HC)), and no mangrove to mixed terrestrial and agricultural vegetation (Khobar (KC)) along with the Indus River and adjacent NE Arabian Sea. Silicate (SiO32–) was the most abundant nutrient, and its concentration increased from the northeast to the southwest monsoon and decreased during the fall intermonsoon. Erosion of the riverbank catchment area, weathering, and sand mining are the major sources of elevated SiO32–. The highest concentration of nitrate (NO3–) was found in the main river channel (KC) throughout the year, with maximum concentration (37.42 ± 5.05 μM) in the river (KC) during the rainy season (SW monsoon) due to the agricultural runoff that resulted in an increase in chlorophyll a. The concentration of nitrite (NO2–) was high in the creek (DC) with mangroves and agricultural runoff input. The concentration of phosphate (PO43–) was high in mangrove-dominated creeks (WK and DC), suggesting litterfall as a major source of PO43− from the creeks. The river with no mangrove cover (KC) indicated that PO43– was a limiting factor. In the case of DSi:DIN ratios, SiO32–was not limited throughout the sampling period for primary production. The chlorophyll a concentration increased from upstream to downstream in the river and was positively correlated with SiO32– and NO3–, resulting in the dominance of diatoms during the SW monsoon. The study confirms that natural sources (river/terrestrial runoff and geomorphological factors) and anthropogenic factors (application of fertilizers, manure, construction of dams, and industrialization) significantly influenced the nutrients and chlorophyll a, both spatially and temporally. On a global scale, SiO32– concentrations in the Indus River during the southwest monsoon were lower than those in the Himalayan rivers (Brahmaputra, Ganges, Huanghe, and Yangtze Rivers). The NO3– concentration is comparable with that of Narmada, Tapti, and Pangani Rivers but lower than that for rivers originating from the Himalayas. Nutrient enrichment and eutrophication in coastal waters were mainly caused by urbanization and population increase, which affect the higher trophic level productivity and fish abundance in the coastal and shelf areas. Therefore, an integrated approach for the management and monitoring of upstream river systems is required for a better future.

From South Asia to the world: embracing the challenge of global sustainable nitrogen management

From South Asia to the world: embracing the challenge of global sustainable nitrogen management

Assessment of the Ecological Security of the Coastal Zone of the Guangdong/Hong Kong/Macao Greater Bay Area

Zhao, W.; Zhao. G.; Yang, J.; Xu, M., and Kou, J., 2020. Assessment of the ecological security of the coastal zone of the Guangdong/Hong Kong/Macao greater bay area. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 287-295. Coconut Creek (Florida), ISSN 0749-0208.With the impact of global climate change and the acceleration of urbanization, the coastal zone of the Guangdong/Hong Kong/Macao Greater Bay area (GBA) faces the pressures of biodiversity reduction, loss of coastal wetlands, eutrophication of coastal waters and frequent marine pollution events, all of which affect the ecology of this environment and threaten high-quality development of the GBA coastal zone. This study looked at the coastal zones adjacent to nine cities in the GBA, and analyzed the temporal and spatial changes in key ecological and environmental factors using remote sensing, field observations and data collection. A pressure-state-response model was used to build coastal zone ecological security evaluation indexes. The resulting assessments based on the ecological security index of each administrative region in the GBA were used to evaluate their ecological security status, diagnose their existing problems and analyze the causes in each of them. The results showed that the state grade of the GBA coastal zone follows a V-shape, with the eastern and western parts in better ecological condition than the central part. With regard to the current management of the coastal ecological environment, this paper suggests six future policies for improvements to coastal protection in an effort to promote high-quality development in GBA coastal zones, including strengthening top-level planning, optimizing port design and strengthening supervision.

Growth and phosphatase activities of Ostreopsis cf. ovata biofilms supplied with diverse dissolved organic phosphorus (DOP) compounds

It is becoming increasingly evident that the use of organic nutrients is widespread among many aquatic phototrophic organisms. Simultaneously, incidents of eutrophication of coastal waters are becoming more common due to rises in organic nutrient loads deriving from anthropogenic activities and natural terrestrial processes. In the northern Adriatic Sea, blooms of the toxic dinoflagellate Ostreopsis cf. ovata are reported as a frequent phenomenon linked to particular environmental conditions, including increased organic nutrient loads. Ostreopsis blooms typically produce a mucilaginous biofilm that can cover all benthic substrata. In order to clarify the role of dissolved organic phosphorus (DOP) in the onset and maintenance of an O. cf. ovata bloom, we investigated the growth rates in the presence of a range of phosphomonoesters (PMEs) (D-fructose 1,6-disphosphate, β-glycerophosphate, α-D-glucose 1-phosphate, guanosine 5’-monophosphate and phytic acid) and phosphodiesters (PDEs) (DNA and RNA). Levels of both phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities were assessed in the O. cf. ovata biofilms. The results showed that O. cf. ovata growth is not inhibited in media containing a wide range of DOP and diverse ratios of PME:PDE compared to those containing inorganic phosphorus. Much of the hydrolytic activity was associated with bacteria and with extracellular polymeric substances (EPSs). Our findings suggest that the success of O. cf. ovata stems from the collective participation of all components of the biofilm (O. cf. ovata, EPSs and bacteria) that allows it to thrive in phosphorus-limited environments, but where the main source of phosphorus is organic.

A real time data driven algal bloom risk forecast system for mariculture management

In eutrophic coastal waters, harmful algal blooms (HAB) often occur and present challenges to environmental and fisheries management. Despite decades of research on HAB early warning systems, the field validation of algal bloom forecast models have received scant attention. We propose a daily algal bloom risk forecast system based on: (i) a vertical stability theory verified against 191 past algal bloom events; and (ii) a data-driven artificial neural network (ANN) model that assimilates high frequency data to predict sea surface temperature (SST), vertical temperature and salinity differential with an accuracy of 0.35oC, 0.51oC, and 0.58 psu respectively. The model does not rely on past chlorophyll measurements and has been validated against extensive field data. Operational forecasts are illustrated for representative algal bloom events at a marine fish farm in Tolo Harbour, Hong Kong. The robust model can assist with traditional onsite monitoring as well as artificial-intelligence (AI) based methods.

Spatial differences in growth rate and nutrient mitigation of two co-cultivated, extractive species: The blue mussel (Mytilus edulis) and the kelp (Saccharina latissima)

Cultivation of extractive species, such as bivalves and seaweeds, provides opportunities for food production while removing excess nutrients in eutrophic coastal waters. However, to optimize these ecosystem services, selecting aquaculture sites that affect growth and nutrient uptake is important. In a transplant experiment we assessed spatial growth patterns of the blue mussel Mytilus edulis and the kelp Saccharina latissima, which were used to estimate nutrient removal. Optimal locations for growth and nutrient extraction differed, mussels grew better in relatively sheltered inner coastal areas, whereas seaweed growth increased in outer more exposed coastal areas. Estimates of mitigatory capacity indicated that under the best available conditions, mussels remove approximately 700 kg N and 6600 kg C ha−1yr−1, whereas seaweed removes approximately 100 kg N and 1000 kg C ha−1yr−1. We identified the importance of site selection for the overall capacity of two extractive species (bivalves and seaweeds) in order to synergistically maximise their growth and nutrient mitigation.

Developing improved methods for identifying the cost-efficient abatement set in coastal water quality protection

Eutrophication of coastal waters is a recognised problem in estuaries around the globe. To analyse cross-boundary water quality management, such as protection of the Baltic Sea, economic nutrient abatement models commonly operate on a large scale, grouping river systems to large catchment areas. Theoretical deliberation suggests that modelling abatement in such a way removes the opportunity of targeting measures to the most vulnerable regions within the catchment, while overestimating the capacity of abatement measures in the upstream areas. However, the implications on designing environmental policy depend on catchment characteristics and the stringency of the abatement targets. In this study a model of the catchment area is built with zones that are an increasing distance away from the coast to show what kind of bias in the optimal abatement set is caused by the assumption of spatial homogeneity. By solving the model with and without the zones for good ecological status at the South-West coast of Sweden, it is shown that while assuming homogeneity prevents from perceiving the abatement measures where they would be the most effective, it also leads to ignoring spatial limitations that are more relevant to a subset of abatement measures, such as the wetlands and buffer zones. Following from the relatively large nitrogen abatement targets, the overall effect of assuming catchment homogeneity is to underestimate the abatement costs and to overestimate the potential of wetlands to reduce nitrogen.

Description of biological wastewater treatment plants of city of Odesa as sources of marine environment nutrient pollution in current period

Biological wastewater treatment plants (the BTPs) of city of Odesa (Northern and Southern Plants) are the most powerful permanent sources of nutrient pollution of coastal waters of Odesa Region of the north-western part of the Black Sea (the NWPBS) and the Khadzhybei Liman. The article includes a comparative analysis of changes, taking place since the beginning of the 21st century, related to the qualitative composition of return water of the Northern and Southern BTPs and the amount of nutrients reaching the marine environment together with such water, as well as the analysis of possible influence of such changes on eutrophication of coastal waters of Odesa Region of the NWPBS and the Khadzhybei Liman. It was established that despite significant decrease (by 1.7 - 2 times) of return water discharged from the BTPs the amount of nitrates and nitrites reaching the marine environment together with such water increased by 4-6 times. At the same time the reduced inflow of organic matter, ammonium nitrogen and phosphates can be observed.
 Treatment facilities of Odesa were put into operation back in the 1970s. They use a then typical technology of biological cleaning of wastewater from nutrient compounds in aeration tanks providing aerobic conditions. The technology is considered as incomplete in terms of nitrogen compounds treatment since its final product includes nitrate nitrogen in large quantities. When reaching the marine environment it is absorbed by algae at the stage of primary production of organic matter and thus is transformed in organic nitrogen again. It was noted that since the coastal waters of Odesa Region of the NWPBS and the Khadzhybei Lyman have a high level of trophicity and currently there is a disbalance between mineral nitrogen and phosphorus concentrations in the water towards insufficiency of mineral nitrogen reserves (as compared with the standard Redfield stoichiometric ratio), additional inflow of nitrates and nitrites in the marine environment together with return water from the BTPs would, in certain circumstances, lead to algal bloom and aggravation of negative eutrophication-related consequences.
 The research allowed making a conclusion that a modern flow sheet of advanced biological cleaning (treatment) of wastewater from nitrogen compounds should be implemented at the Northern and Southern BTPs in order to reduce the inflow of nitrates in the marine environment. Such flow sheet should ensure both nitrification and denitrification processes.