New study on resonant impacts of increased organic pollution, nutrition and climate change on primary productivity in coastal waters of Cat Ba - Ha Long
Primary productivity of coastal waters
Primary productivity is the amount of organic matter produced in a unit of time per unit area, or simply the biomass production capacity of a floating organism. Primary productivity plays an important role in the food chain, biogeochemical processes and marine fish. The results of the study have shown that primary productivity varies over time and space, depending on major factors such as carbon dioxide (CO2), light, nutrition, and other environmental factors such as temperature, depth, wind, and plankton.
The coastal zone is a place where strong interaction between continental-marine processes takes place and is greatly affected by human activities. This is the place with the most abundant source of nutrients from the continent, so the coastal estuary is often the place with the highest primary productivity. However, the water environment in this area is also vulnerable due to the increase in exploitation and resource use, and the increase in pollutants from the continent. The increase in primary productivity in coastal areas has a positive impact on the environment and ecosystems within a certain limit, when these thresholds are exceeded, eutrophication occurs, causing oxygen deficiency, killing marine organisms, increasing the risk of pollution and environmental degradation in coastal areas. Until now, studies, assessments, and forecasts on the impacts of climate change (increase in temperature, rising water level) on primary productivity in Vietnamese waters have not received enough attention, especially research on the combined effects of increased pollutants from human activities and climate change on primary productivity in coastal waters.
New research - an important scientific argument
The coastal waters of Cat Ba - Ha Long, where there is biodiversity, many specific ecosystems, marine biological resources have high economic value and great potential for the development of service tourism and aquaculture. In recent years, the socio-economic activities of Hai Phong city and Quang Ninh province have taken place very strongly. Therefore, the Cat Ba - Ha Long area is a place that clearly shows the impacts of human activities such as spatial change, increasing sources of organic pollutants and nutrients to the coastal area. These impacts may be exacerbated in the context of climate change as temperatures rise and sea levels rise. However, the issue of human impacts on primary productivity in coastal areas has not been studied.
Stemming from practical needs and in order to provide important scientific bases and documents for the sustainable development of the coastal area of Cat Ba - Ha Long, Dr. Vu Duy Vinh and his colleagues from the Institute of Natural Resources and Marine Environment conducted the project: "Research on the impact of the increase in organic and nutrient pollution sources from human activities and climate change on primary productivity in the coastal waters of Cat Ba - Ha Long" (code: VAST05.05/21-22).
In particular, scientists have successfully assessed the development and increasing trend of sea temperature and sea level in the study area over the past 60 years (from 1960 to 2020). In particular, the trend of rapid increase in the past 20 years of sea level temperature (up to 0.093°C/year in Hai Phong coastal area and over 0.1°C/year in Quang Ninh waters) and sea level (7mm/year in Hai Phong waters and 5.4 - 11.2 mm/year in Quang Ninh waters), (Figure 1). Also in this study, the team assessed and forecasted the impacts due to the increase in nutrient/organic sources from human activities and climate change (increase in temperature and water level) in the Cat Ba - Ha Long area. Accordingly, the effects of increasing nutrient, organic, temperature, and water levels in the 2025, 2030 and 2050 scenarios did not significantly change the distribution of primary productivity in the study area. In some areas such as the middle and southeast of Ha Long Bay and Cat Ba Bay, the results of the analysis show that these resonant effects also show different degrees by season and each region (Figure 2). However, these changes (increase/decrease) are only about 0.001-0.003 gC/m3/day.
Figure 1. The trend of sea level increase in the period 1960-2020; (a) and sea water temperature in the period 1995-2020; (b) in the coastal waters of Hai Phong - Quang Ninh
Figure 2. Primary productivity in the coastal area of Cat Ba - Ha Long at the surface level (low tide) under the combined influence of increasing nutrient/organic sources from human activities and climate change (rising water temperature/sea level) in spring according to a number of scenarios (a - 2021; b- forecast for 2025, c - Forecast to 2030; d- Forecast to 2050)
Dr. Vu Duy Vinh shared: The new research results have updated data on the trend of sea level rise, sea temperature increase in Hai Phong - Quang Ninh waters in general and Cat Ba - Ha Long in particular. This is an important reference, valuable in science as well as application in management. In addition, assessments and forecasts of the impacts of humans, climate change on the environment and primary productivity in the study area will help relevant units make reasonable and scientific decisions for socio-economic development associated with environmental protection for the goal of sustainable development. The scientific products of the project published in prestigious domestic and foreign journals will be valuable references for related research. Dr. Vinh affirmed that these research results are only the first step, in order to systematically assess the resonant effects of human activities and climate change on primary productivity, it is necessary to have a more comprehensive and comprehensive study with many measurements and surveys and hopes that his team will develop this research well in the future.
Translated by Phuong Ha
Link to Vietnamese version
