School of Natural Sciences, Macquarie University, North Ryde, NSW, 2109, Australia.
School of Natural Sciences, Macquarie University, North Ryde, NSW, 2109, Australia; Sydney Institute of Marine Science, Mosman, NSW, 2088, Australia.
Environ Pollut. 2023 Jan 1;316(Pt 2):120614. doi: 10.1016/j.envpol.2022.120614. Epub 2022 Nov 7.
Over the last century, human activities have increased the amount of nutrients inputs to terrestrial and aquatic ecosystems. These activities have altered nitrogen (N) and phosphorus (P) cycling, causing substantial changes in ecosystem function such as provision of clean air and water. Strategies that reduce and remove excess nutrients are urgently needed to remediate impacted systems. Reef-forming shellfish (oysters and mussels) can play a crucial role in nutrient cycling, particularly in N removal from aquatic systems by providing substrate for microbial colonisation and enhancing microbial denitrification in the surrounding sediments. However, the potential for shellfish to enhance nutrient cycling (and denitrification) will likely vary spatially and in response to several environmental factors. Here, we used 1) a qualitative analysis to review nutrient processes occurring on shellfish; and 2) a meta-analysis to evaluate the influence of shellfish on benthic metabolism and nutrient cycling in surrounding sediments, and how that is influenced by environmental factors such as grain size, seasonality, water body type, and tidal position. Overall, we found that shellfish increased oxygen consumption, with consequent release of ammonia (NH) and phosphate (PO) from shellfish and their surrounding sediments. These parameters did not depend on grain size, water body type and tidal height, but the release of PO was variable between seasons, being highest during summer and autumn. Shellfish presence also enhanced denitrification measured as dinitrogen gas (N) efflux on both reefs and sediments. Denitrification was highest in lagoons; in sandy sediments; and during the warmest season (summer). Thus, our findings highlight that environmental context can mediate the effects of shellfish reefs on sediment function. This information is important for managers seeking to use these animals as an effective bioremediation tool.
在上个世纪，人类活动增加了陆地和水生生态系统的营养物质输入量。这些活动改变了氮（N）和磷（P）的循环，导致生态系统功能发生了重大变化，例如提供清洁的空气和水。为了修复受影响的系统，迫切需要减少和去除过量营养物质的策略。造礁贝类（牡蛎和贻贝）可以在营养物质循环中发挥关键作用，特别是通过为微生物定殖提供基质并增强周围沉积物中的微生物反硝化作用，从而从水生系统中去除 N。然而，贝类增强营养物质循环（和反硝化作用）的潜力可能会因空间而异，并受到多种环境因素的影响。在这里，我们使用 1）定性分析来审查贝类上发生的营养过程；和 2）元分析来评估贝类对周围沉积物中底栖代谢和营养物质循环的影响，以及环境因素（如粒度、季节性、水体类型和潮汐位置）如何影响这种影响。总的来说，我们发现贝类增加了耗氧量，从而导致贝类及其周围沉积物中氨（NH）和磷酸盐（PO）的释放。这些参数不依赖于粒度、水体类型和潮汐高度，但 PO 的释放在季节之间存在差异，夏季和秋季最高。贝类的存在还增强了硝态氮（N）作为二氮气体（N）通量的反硝化作用，无论是在珊瑚礁还是沉积物上。反硝化作用在泻湖中最高；在沙质沉积物中；在最温暖的季节（夏季）最高。因此，我们的研究结果强调了环境背景可以调节贝类礁对沉积物功能的影响。对于寻求利用这些动物作为有效生物修复工具的管理者来说，这些信息非常重要。
