Skip to main content


Log in

Does the Size Structure of Venerid Clam Populations Affect Ecosystem Functions on Intertidal Sandflats?

  • Published:
Estuaries and Coasts Aims and scope Submit manuscript


Estuaries are hotspots for biogeochemical cycling, with bivalves integral to many ecosystem functions. Anthropogenic activities often cause reductions in biomass and abundance of key bivalve species in estuaries worldwide. Large bivalves are particularly vulnerable due to their slow growth, low replacement rates and propensity for being overharvested; however, there is a paucity of studies on how declines in bivalve size and density affect ecosystem functions. An in situ manipulative experiment was conducted on a New Zealand intertidal sandflat in late summer (March to May 2017) to investigate changes in ecosystem functions (sediment nutrient regeneration, primary production, community metabolism and microbial activity) across a biomass gradient (0–4 kg wet weight m−2) of small (shell length (SL) < 25 mm) and large (SL > 30 mm) venerid clams (Austrovenus stutchburyi). Bird predation reduced the biomass of small clams, so ecosystem functions were normalised to per kilogramme of wet weight. Small clams significantly increased gross primary production by ~ 3× and net primary production by ~ 7× compared with large clams. Small clams also doubled activity rates of microbial enzymes associated with nutrient cycling and organic matter breakdown (leucine aminopeptidase and alkaline phosphatase). By contrast, nitrate/nitrite flux was significantly greater with large clams. Macrofaunal species diversity and mud content also influenced benthic nutrient cycling, possibly due to increased sediment reworking that alters solute flux rates. Results demonstrate how different size classes of venerid clams influence complementary ecosystem functions. Accordingly, a skewed size class distribution of bivalves will reduce the productivity and functioning of intertidal sandflats.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or Ebook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2

Similar content being viewed by others


Download references


We would like to thank everyone involved in the field sampling and laboratory work, Jack Hall, Sorrel O’Connell-Milne, Stina Kolodzey and Linda Groenewegen. We gratefully acknowledge the two anonymous reviewers whose comments and feedback greatly improved the manuscript.


This work was funded by Sustainable Seas New Zealand Tipping Points project (CO1X1515), Environment Southland and a scholarship from the New Zealand Coastal Society.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Samuel Thomas.

Additional information

Communicated by Judy Grassle

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Thomas, S., Pilditch, C.A., Thrush, S.F. et al. Does the Size Structure of Venerid Clam Populations Affect Ecosystem Functions on Intertidal Sandflats?. Estuaries and Coasts 44, 242–252 (2021).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: