굴 양식수역의 환경용량 산정 -I. 생태계 모델을 이용한 거제 · 한산만 굴 먹이 공급량 추정

We investigated assessments of calorie production and energy efficiencies of phytoplankton in Gwangyang, Jaran, and Geoje-Hansan bays in southern Korea, based on seasonal field measurements data for particulate organic carbon (POC), macromolecular compositions, calorie contents, and primary production. Our findings revealed that Geoje-Hansan Bay consistently exhibits higher POC concentrations compared to Gwangyang and Jaran bays, except during the summer season. The observed seasonal variations in POC concentrations and primary productions indicated distinct factors influencing POC distribution among the bays, which varies with the seasons. Macromolecular compositions displayed notable patterns, with Gwangyang Bay exhibiting pronounced seasonal variations, Jaran and Geoje-Hansan bays showing stable carbohydrate (CHO) dominance, and Gwangyang Bay displaying protein (PRT) dominance influenced by river-borne nutrients. Analysis of calorie content revealed that Geoje-Hansan Bay exhibited the highest calorie content, suggesting a more favorable physiological state of phytoplankton compared to Gwangyang and Jaran bays. Estimations of annual primary production and calorie production demonstrated regional variations, with Geoje-Hansan Bay having the highest values followed by Jaran Bay and Gwangyang Bay. These differences in primary production and calorie production reflect the diverse ecological conditions and nutrient availability specific to each bay. Interestingly, Gwangyang Bay demonstrated the highest energy efficiency, producing more calories per unit of carbon compared to the other two bays, potentially due to the influence of different dominant phytoplankton communities. This study enhances our understanding of ecosystem dynamics and ecological characteristics among the three bays, emphasizing the importance of considering seasonal variations and specific bay characteristics in investigating biogeochemical processes, energy flow, and ecosystem functioning. The findings contribute valuable insights for the sustainable management of coastal ecosystems and aquaculture practices.

The contribution of microphytobenthos to total productivity in upper Narragansett Bay, Rhode Island

黄土高原生态系统服务权衡与协同时空变化及影响因素——以延安市为例

Phytoplankton constitutes an important dietary item of oysters in suspended longline aquaculture systems. Primary productivity and the community structure of phytoplankton, as well as hydrographic and nutritional conditions of the water column, were monitored monthly in Geoje-Hansan Bay on the southern coast of Korea between July 2013 and July 2014 to determine the seasonal variation patterns of productivity and structures of phytoplankton assemblages. All measured physicochemical and biological components exhibited temporal variabilities common to all four sampling sites within the bay system. The hydrographic features were characterized by a summer stratified and fall–winter well-mixed structure of the water column. Daily primary productivity in the bay (0.16–2.88 g C m–2 d–1) peaked in summer; it displayed a unimodal cycle, and the most dominant phytoplankton group shifted from diatoms to dinoflagellates. Canonical correspondence analysis, based on environmental factors and the phytoplankton community, enabled the identification of seasonal patterns of phytoplankton assemblage in relation to temporal variations of hydrographic and nutritional conditions. Results indicated that increase of the watercolumn stability and enhanced nutrient input by freshwater discharge during the summer monsoon and possible upward flux from bottom sediment led to the peaking primary productivity and diatom-dominated community during that time, supporting high annual productivity (371 g C m–2 yr–1). Our findings suggest that seasonal properties of hydrodynamics and nutritional conditions play a key role in determining the primary productivity and structuring of the phytoplankton community. Summer peaks in productivity and diatom dominance most likely ultimately determine oyster growth and the final success of aquaculture.

We evaluated relative levels of paleo‐primary productivity in eastern Lake Ontario during the past ~10,000 yr via analysis of inorganic and organic sediment from the Rochester Basin. There was significant natural variability in primary production correlative with Holocene climate change. The cold post‐Younger Dryas interval (~10–9.4 ka) was a time of minimal levels of primary production. The warm Holocene Hypsithermal interval (~9.4–5.3 ka) had much higher levels of primary production but was more variable, including five well‐defined cycles that have an average period of ~750 yr. The largest negative anomaly in primary productivity occurred during the 8.2‐ka climate event (~8.4–8.0 ka), a time of cold, dry conditions. Another negative anomaly occurred in association with the Nipissing flood (~6.3–5.3 ka), which triggered a regional cooling event. The cool Holocene Neoglacial interval (~5.3 ka to ~1850 A.D.) was characterized by lower, but more stable, levels of primary production, as well as by a cessation of calcite precipitation and the onset of diatom productivity. During the historic interval (~1850–1940 A.D.), there was a dramatic increase in primary production to unprecedented levels over the past 10,000 yr, as well as a 30–fold increase in sediment accumulation rates. These large, abrupt changes occurred in response to regional deforestation, anthropogenic nutrient loading, and increased chemical weathering due to acid rain. We project that, during 21st century global warming, eastern Lake Ontario will evolve into an ecosystem similar to that during the Holocene Hypsithermal.

Seasonal coupling between riverborne nutrients, net productivity and hypoxia

Monitoring data (1999 to 2012) and data from a 2 wk field study at a seasonally strat- ified station in the Aarhus Bight near the Danish coast were used to demonstrate that the vertical distribution of photosynthesis influences both water column oxygen conditions and the fate of the organic material produced. The primary production (PP) occurring below the surface layer, i.e. in the pycnocline-bottom layer (PBL), is shown to contribute significantly to total PP. Oxygen concen- trations in the PBL are shown to correlate significantly with the deep primary production (DPP) as well as with salinity, phosphate loading, wind and transparency in the surface layer. The phyto- plankton communities detected in the surface layer and PBL during the field study were very dif- ferent. Large cells, especially Ceratium spp., dominated in the PBL, while small diatoms, mainly Proboscis alata, dominated in surface waters. On the basis of chlorophyll-normalised photo - synthetic parameters and variable fluorescence, it is shown that the 2 populations were physio - logically distinct. The population in the PBL was photosynthetically active and adapted/ acclimated to lower light than the population in the surface layer. Sinking rates (based on sedi- ment trap collections) of carbon and nitrogen were highest in the PBL. Lyngsgaard et al. (2014; Limnol Oceanogr 59:1679�1690) have demonstrated that the vertical distribution of PP in this region is influenced by anthropogenic nutrient loading. Thus, the present study indicates that eutrophication effects may include changes in the structure of planktonic food webs and element cycling in the water column, both brought about through an altered vertical distribution of PP.

An apparent proliferation of filamentous algal blooms (FABs) in pristine lakes around the world is a source of concern. However, little is known about the predominant drivers and effects of such FABs on lake ecosystems. We observed FABs in a large clear-water lake (Bear Lake, UT/ID, USA) and analyzed long-term lake monitoring data and algal stable isotopes for changes in climate, food webs and anthropogenic nutrient loading, respectively, as potential local drivers of FAB formation. Furthermore, we quantified in situ metabolism rates on rocks with and without FABs at two locations. Long-term monitoring data revealed increasing summer water temperatures (2009 to 2020) and decreasing winter ice cover (1923 to 2021). The FABs had δ15N values that were higher than 0 ‰, indicating a potential nutrient influx to Bear Lake from livestock or human waste. Climate change and anthropogenic nutrients may thus have facilitated FAB occurrence. Contrary to expectation, the FABs exhibited significantly lower gross primary production rates compared to low-biomass periphyton communities, indicating potentially negative effects of FAB proliferations on lake food webs. Our results highlight the need for expanding lake monitoring programs to include littoral zones to detect and mitigate changes occurring in lakes.

Heterotrophic consumption may mask increasing primary production fuelled by anthropogenic nutrient loading in the northern Arabian/Persian Gulf

Summary Lakes Michigan and Huron, which are undergoing oligotrophication after reduction of phosphorus loading, invasion by dreissenid mussels and variation in climate, provide an opportunity to conduct large‐scale evaluation of the relative importance of these changes for lake productivity. We used remote sensing, field data and an information‐theoretic approach to identify factors that showed statistical relationships with observed changes in chlorophyll a (chla) and primary production (PP). Spring phosphorus (TP), annual mean chla and PP have all declined significantly in both lakes since the late 1990s. Additionally, monthly mean values of chla have decreased in many but not all months, indicating altered seasonal patterns. The most striking change has been the decrease in chla concentration during the spring bloom. Mean chlorophyll a concentration was 17% higher in Lake Michigan than in Lake Huron, and total production for 2008 in Lake Michigan (9.5 tg year−1) was 10% greater than in Lake Huron (7.8 tg year−1), even though Lake Michigan is slightly smaller (by 3%) than Lake Huron. Differences between the lakes in the early 1970s evidently persisted to 2008. Invasive mussels influenced temporal trends in spring chla and annual primary production. However, TP had a greater effect on chla and primary production than did the mussels, and TP varied independently from them. Two climatic variables (precipitation and air temperature in the basins) influenced annual chla and annual PP, while the extent of ice cover influenced TP but not chla or primary production. Our results demonstrate that observed temporal patterns in chla and PP are the result of complex interactions of P, climate and invasive mussels.

Understanding the spatiotemporal characteristics of trade-offs and synergies among multiple ecosystem services (ESs) is the basis of sustainable ecosystem management. The ecological environment of valley basins is very fragile, while bearing the enormous pressure of economic development and population growth, which has damaged the balance of the ecosystem structure and ecosystem services. In this study, we selected two typical valley basins—Guanzhong Basin and Hanzhong Basin—as study areas. The spatial heterogeneity of trade-offs and synergies among multiple ESs (net primary production (NPP), habitat quality (HQ), soil conservation (SC), water conservation (WC), and food supply (FS)) were quantified using the correlation analysis and spatial overlay based on the gird scale to quantitatively analyze and compare the interaction among ESs in two basins. Our results found that: (1) Trade-offs between FS and other four services NPP, HQ, SC, and WC were discovered in two basins, and there were synergistic relationships between NPP, HQ, SC, and WC. (2) From 2000 to 2018, the conflicted relationships between paired ESs gradually increased, and the synergistic relationship became weaker. Furthermore, the rate of change in Guanzhong Basin was stronger than that in Hanzhong Basin. (3) The spatial synergies and trade-offs between NPP and HQ, WC and NPP, FS and HQ, SC and FS were widespread in two basins. The strong trade-offs between pair ESs were widly distributed in the central and southwest of Guanzhong Basin and the southeast of Hanzhong Basin. (4) Multiple ecosystem service interactions were concentrated in the north of Qinling Mountain, the central of Guanzhong Basins, and the east of Hanzhong Basin. Our research highlights the importance of taking spatial perspective and accounting for multiple ecosystem service interactions, and provide a reliable basis for achieving ecological sustainable development of the valley basin.

과밀양식으로 생산성이 저하되고 있는 거제 <TEX>$\cdot$</TEX> 한산만의 안정적이고 지속적인 굴 생산방안을 제시하기 위하여 생태계 모델을 이용하여 먹이 공급량을 추정하였고, 양식 굴의 여수율과 chloro-phyll <TEX>$\alpha$</TEX> 농도로부터 먹이 요구량을 계산하여 양식 수용력을 산정한 결과는 다음과 같다. 수확 크기별 굴의 먹이 요구량은 습중량 4g의 알굴인 경우 1.40~4.82mgC/ind./day (평균 2.49mgC/ind./day), 습중량 7g의 알굴인 경우 1.96-6.77mgC/ind./day (평균 3.50mgC/ind./day) 범위로 나타나 알굴의 습중량이 증가할수록 먹이 요구량도 크게 나타났다. 월별로는 2월이 가장 작았고, 9월이 가장 크게 나타났다. 월별 먹이 공급량을 월별 먹이 요구량으로 나누어 수확 크기별 수용력을 산정한 결과 2월이 평균 6.10 ton/ha로 최저 수용력을 나타내었고, 4월이 14.91 ton/ha로 최대 수용력을 나타내었다. 거제 <TEX>$\cdot$</TEX> 한산만의 알굴 생산량은 9ton/ha로 최대 수용력의 <TEX>$60\%$</TEX> 수준이나 지속적 생산을 위해서는 임계 수용력인 2월의 6.1ton/ha와 통계자료에 의한 최대 생산량 5.5ton/ha를 감안하여 현재 시설량을 <TEX>$32\%{\~}39\%$</TEX> 정도 줄여야 할 것으로 판단되었다. A 3D hydrodynamic-ecological coupled model was applied to estimate carrying capacity in Geoje-Hansan Bay where is one of the most important oyster culturing grounds in Korea. We considered the carrying capacity as the difference between food supply to the oysters and food demand, considering monthly difference of the actual growth. The food supply to the system was determined from the results of the model simulation (tidal exchange and chlorophyll <TEX>$\alpha$</TEX>) over the culturing period from September to May of the following year. The food demand was estimated from the food concentration (chlorophyll <TEX>$\alpha$</TEX>) multiple the filtration rate of oysters that is considered monthly different growth rate of oysters and food concentration. The values of carrying capacity for the system varied from 6.1 ton/ha (minimum carrying capacity) in february to 14.91 ton/ha (maximum carrying capacity) in April of marketable size oysters (>4 g wet-tissue weight) depending on temporal variations in the food supply. The oyster production calculated from present facilities was 9 ton/ha in wet-tissue weight in Geoje-Hansan Bay. This value corresponded to <TEX>$60\%$</TEX> of maximum carrying capacity of the system. The optimal carrying capacity without negatively affecting on oyster production was 5.5 ton/ha when calculated from annual statistic data and 6.1 ton/ha when determined by this study. These results suggest that it must be reduced <TEX>$32\%$</TEX>~<TEX>$39\%$</TEX> of oyster facilities in the system.

Eutrophication and heavy metal pollution in the Flensburg Fjord: A reassessment after 30 years

Effect of sewage nutrients on algal production, biomass and pigments in tropical tidal creeks

Hydrography of the eastern Arabian Sea and associated chemical and biological responses were studied during the withdrawal phase of summer monsoon 2003. The shelf region off the southwest coast of India (10°N–15°N) continued to exhibit upwelling of colder ( 2.0 μM, phosphate >0.8 μM, silicate >4.0 μM) and relatively low oxygenated waters (~180 μM). The vertical advection of nutrients, coupled with anthropogenic terrestrial inputs, enhanced the levels of chlorophyll and primary productivity near the coastal margin off Cochin. The influence of both natural and anthropogenic nutrient loadings on the coastal system of the western continental shelf of India leads to eutrophication and hypoxia with negative impacts on the environment in general and fisheries in particular.