The effect of adult cockles, Austrovenus stutchburyi, on sediment transport

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作   者：

Judi E. Hewitt;  Rebecca V. Gladstone-Gallagher;  Li Hao Yeoh;  Simon F. Thrush; 

作者机构：

New Zealand;  University of Auckland;  25a Princes St;  Auckland 1010; 

关键词：

Resuspension;  Sediment stability;  Feedback loops;  Species interactions;  Intertidal;  Sediment transport; 

期刊名称：

Journal of experimental marine biology and ecology

i s s n：

0022-0981

年卷期：

2024 年 570 卷 Jan. 期

页   码：

151975.1-151975.12

页   码：

摘   要：

Sediment transport and resuspension are essential processes in soft-sediment environments that mediate shellfishpopulation dynamics, water column turbidity, and estuary geomorphology at multiple scales. Adult cockles,Austrovenus stutchburyi (in New Zealand), are key organisms on intertidal sand flats that influence sedimentproperties, and their removal could impact the stability of the seabed and affect crucial feedback processes in thissystem. We conducted a field experiment to explore our hypothesis that the loss of adult cockles will increasesediment transport and resuspension non-linearly. Changes in sediment transport regimes will then influence theproperties of sediment such as grain size, organic content, and chlorophyll a content. We also expected that thedirection and magnitude of this effect would depend on the varying environmental characteristics across thesites, such as hydrodynamic activity and sediment grain size. We excluded adult cockles from 3 × 3 m intertidalplots at 15 sites across a natural adult cockle density gradient (300–3500 ind/m2). After seven months, sedimenttraps were deployed in exclusion and control plots to measure the sediment transported over two tidal cyclesassociated with the bedload and water column with differing densities of adult cockles. Adult cockle density wasa significant predictor in all models to explain sediment transport and accounted for the largest proportion ofvariability explained. Relationships between cockle density and sediment transport changed between sites andover time. In these situations, simple linear relationships were not always apparent due to the interacting effectsof cockle density, hydrodynamic process, and sediment characteristics. The influence of adult cockles on sedimenttransport was also affected by the standing stock of microphytobenthos and interacted with the mudcontent in their surrounding environment. Our study demonstrates the existence of an important feedback betweenadult cockle density, sediment stability and sediment transport that is mediated by hydrodynamic processesand sediment characteristics.