Changes in benthic community structure and sediment characteristics after natural recolonisation of the seagrass Zostera muelleri

Carolyn J Lundquist,Samantha M Parkes,Tracey C Jones,Richard H Bulmer

doi:10.1038/s41598-018-31398-2

Carolyn J Lundquist, Samantha M Parkes + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-31398-2

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Abstract

Macrofauna are important contributors to estuarine ecosystem services within and outside of seagrass beds. Here we documented the natural recolonisation of a temperate seagrass (Zostera muelleri) community over 15 years in an urban estuary (Waitemata Harbour, North Island, New Zealand). We also investigated the change in macrofaunal communities in relation to seagrass cover over time, from transition from bare sandflat to seagrass. Colonisation by seagrass was associated with an increase in macrofaunal species diversity (from an average of 32 species per core in 2001 to 46 species per core in 2015) and abundance (from 482 to 2273 individuals per core), as well as an increase in sediment mud (from 4.09% to 12.37%) and organic matter content (from 0.90% to 1.41%). The most abundant species within both seagrass and adjacent unvegetated sandflat were similar, the polychaetes Heteromastus filiformis, Aricidea sp., and Prionospio aucklandica, and the amphipod Paracalliope novizealandiae. The difference in macrofaunal community structure between seagrass and unvegetated sandflat was primarily associated with higher abundance of P. novizealandiae and lower abundance of Pseudopolydora sp. in seagrass. A successional effect was observed in macrofaunal communities over the 15 years following seagrass expansion, primarily associated with an increase in the abundance of Aricidea sp., H. filiformis, and P. novizealandiae, and a reduction in the abundance of the bivalve Linucula hartvigiana. This study is the first to document long-term changes in seagrass and their associated communities during a natural recolonisation event, providing insight into timeframes required both for the regrowth of a seagrass meadow from initial colonisation of individual patches, as well as the trajectories and timeframes of change from a sandflat to a seagrass-associated macrofaunal community. This research enhances our understanding of how changes in seagrass distributions due to seagrass loss or restoration may affect macrofaunal community composition and ultimately ecosystem function.

Highlights

Seagrass beds are a major component of estuarine and coastal ecosystems, influencing a number of important ecosystem services, including coastal stabilisation, nutrient and carbon cycling and storage, and trophic transfer[1,2,3]
A number of seagrass meadows in New Zealand are rebounding, with increases in seagrass area observed in recent decades[22,23]
Natural recolonisation of Z. muelleri has been detected in recent decades at a long-term estuary monitoring site within the Waitemata Harbour, with the area adjacent to the monitoring site containing few remnant patches of 40 ha of mostly contiguous intertidal seagrass meadow in 2015

Summary

Introduction

Seagrass beds are a major component of estuarine and coastal ecosystems, influencing a number of important ecosystem services, including coastal stabilisation, nutrient and carbon cycling and storage, and trophic transfer[1,2,3]. Natural recolonisation of Z. muelleri has been detected in recent decades at a long-term estuary monitoring site within the Waitemata Harbour, with the area adjacent to the monitoring site containing few remnant patches of 40 ha of mostly contiguous intertidal seagrass meadow in 2015 This natural recolonisation provides an opportunity to fill important gaps in our understanding of the response trajectory of benthic communities to seagrass recolonisation. This is valuable given the interest in understanding the role of seagrass not just in providing habitat structure and supporting high species richness, and in regard to other ecosystem services provided by seagrass-associated communities such as nutrient and carbon cycling and storage, and trophic transfer[1,32]. This research will enhance our understanding of timeframes and trajectories of macrofaunal communities associated with natural recolonisation by seagrass meadows, and how changes in seagrass distributions due to seagrass loss or restoration may affect macrofaunal species richness, abundance, and community composition, resulting in changes in ecosystem function

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