胶州湾菲律宾蛤仔生态容量评估及其碳汇功能

Evaluation of ecological carrying capacity and functions of Manila clam, Ruditapes philippinarum in Jiaozhou Bay

中文关键词: 菲律宾蛤仔  Ecopath模型  生态容量  碳收支  胶州湾

英文关键词: Ruditapes philippinarum  Ecopath model  Ecological carrying capacity  Carbon budget  Jiaozhou Bay

中文摘要:

      胶州湾是我国重要的菲律宾蛤仔(Ruditapes philippinarum)养殖基地，为探究湾内菲律宾蛤仔的生态容量及其碳汇功能，本研究采用Ecopath模型法评估了胶州湾菲律宾蛤仔的生态容量，并利用Ecosim模块动态分析了菲律宾蛤仔生物量扩大对胶州湾生态系统结构与功能特征的潜在影响，同时估算了胶州湾菲律宾蛤仔个体及种群水平的碳收支情况。结果显示，胶州湾菲律宾蛤仔的生态容量为239.9 t/km2，虽然整体水平尚未达到生态容量，但局部养殖区域已远超出了菲律宾蛤仔的生态容量；当胶州湾菲律宾蛤仔生物量从当前增加至生态容量时，生态系统总流量、容量、优势度和循环指数分别提高了16.0%、3.9%、47.1%和103.0%，而熵值降低了10.4%，表明此时生态系统具有更高的成熟度与稳定性，但菲律宾蛤仔生物量扩大至生态容量10倍时会对生态系统产生不利影响甚至崩溃；菲律宾蛤仔个体在1个养殖周期内约摄取3 310.1 mg C，其中约46.2%的碳沉降至海底，约13.2%的碳通过收获移出，如按菲律宾蛤仔生物量达到生态容量时计算，胶州湾每年将有1.5万t碳以生物沉积形式沉降至海底，有0.6万t碳以收获形式移出。研究结果为指导菲律宾蛤仔增养殖产业的健康可持续发展、阐明菲律宾蛤仔的碳汇功能提供了理论依据与数据支撑

英文摘要:

      Bivalve filter feeders, such as oysters, clams, and scallops, are an economically important species in China, with a total production of up to 14.8×106 tons in 2020, accounting for more than 69.3% of mariculture production. In recent years, the density and scale of shellfish mariculture have continued to increase in some areas owing to economic benefits. The crude farming strategies have a series of negative effects on the cultured organisms and marine ecosystems, such as inhibiting the individual growth rate and increasing individual mortality. The negative effects could then lead to the attenuation of phytoplankton, changing the structure of the phytoplankton community and benthic environment. To manage shellfish farms and the industry properly, it is important to understand the interaction between shellfish aquaculture and the marine environment and evaluate the ability of the marine ecosystem to support shellfish production. At the ecosystem level, the carrying capacity of shellfish is defined as the maximum mariculture density that does not significantly affect the structure and function of marine ecosystems. To evaluate the ecological carrying capacity of shellfish, a method that assesses the overall impact of cultured shellfish on the structure, function, and other functional groups of the ecosystem is required. Based on the principle of nutrition dynamics, the Ecopath model (Ecopath with Ecosim software, Version 6.5) is a scientific and effective tool for evaluating the ecological carrying capacity of shellfish from the perspective of material and energy balance, and fully considers predation, competition, and ecological transformation efficiencies between functional groups. The Ecopath model has been widely used to evaluate the ecological carrying capacity of shellfish in mariculture ecosystems. In addition to their important economic value, bivalve filter feeders play an important ecological role in carbon sequestration, storage, and water purification by ingesting particles and changing the nutrient cycle. In offshore ecosystems, the primary productivity is very high. Filter-feeding bivalves ingest a large amount of phytoplankton to convert particulate organic carbon into feces or pseudo-feces and accelerate the transportation of organic carbon to the seabed. Moreover, calcium carbonate shells are formed through absorption of inorganic carbon from seawater, which plays an important role in long-term carbon storage. Jiaozhou Bay is an important aquaculture base for the Manila clam, Ruditapes philippinarum, in North China. Studies have found that the cultivation of Manila clams caused disturbance to the benthic ecosystem of Jiaozhou Bay. To explore the ecological carrying capacity and ecological service functions of R. philippinarum in the bay, Ecopath with Ecosim models were applied, and the effects of further expansion of clam biomass on the community structure and functional characteristics of the Jiaozhou Bay ecosystem were evaluated. Furthermore, the effects of Manila clam aquaculture on carbon cycling were quantified. Results showed that: The ecological carrying capacity of R. philippinarum in Jiaozhou Bay was 239.9 t/km2; the average biomass of cultured clam has not yet reached the ecological carrying capacity, but the clam biomass in some areas has far exceeded this limit. When the clam biomass increased up to the level of the ecological carrying capacity, the total system throughput, capacity, ascendency, and Finn cycling index would also increase by 16.0%, 3.9%, 47.1%, and 103.0%, respectively, whereas the entropy would decrease by 10.4%, suggesting that the increase in clam biomass would lead to an increase in system maturity and stability; however, continued expansion to 10 times the ecological carrying capacity would adversely affect the ecosystem. At the individual level, a clam ingested approximately 3310.1 mg of carbon during a farming cycle, of which approximately 46.2% was deposited and 13.2% was removed through harvesting; at the population level (scaled to ecological carrying capacity), 15 000 tons of carbon could be deposited, and 6000 tons be harvested annually. These results provide theoretical guidance for the sustainable development of clam aquaculture and its ecological service functions.