Using transplantation to restore seagrass meadows in a protected South African lagoon

Katie M Watson; Deena Pillay; Sophie von der Heyden

doi:10.7717/peerj.16500

Using transplantation to restore seagrass meadows in a protected South African lagoon

PeerJ. 2023 Nov 29:11:e16500. doi: 10.7717/peerj.16500. eCollection 2023.

Authors

Katie M Watson¹, Deena Pillay², Sophie von der Heyden^{1

3}

Affiliations

¹ Department of Botany and Zoology, University of Stellenbosch, Stellenbosch, South Africa.
² Marine and Antarctic Centre for Innovation and Sustainability, Department of Biological Sciences, University of Cape Town, Cape Town, South Africa.
³ School of Climate Studies, University of Stellenbosch, Stellenbosch, South Africa.

Abstract

Background: Seagrass meadows provide valuable ecosystem services but are threatened by global change pressures, and there is growing concern that the functions seagrasses perform within an ecosystem will be reduced or lost without intervention. Restoration has become an integral part of coastal management in response to major seagrass declines, but is often context dependent, requiring an assessment of methods to maximise restoration success. Here we investigate the use of different restoration strategies for the endangered Zostera capensis in South Africa.

Methods: We assessed restoration feasibility by establishing seagrass transplant plots based on different transplant source materials (diameter (ø) 10 cm cores and anchored individual shoots), planting patterns (line, dense, bullseye) and planting site (upper, upper-mid and mid-intertidal zones). Monitoring of area cover, shoot length, and macrofaunal diversity was conducted over 18 months.

Results: Mixed model analysis showed distinct effects of transplant material used, planting pattern and site on transplant survival and area cover. Significant declines in seagrass cover across all treatments was recorded post-transplantation (2 months), followed by a period of recovery. Of the transplants that persisted after 18 months of monitoring (~58% plots survived across all treatments), seagrass area cover increased (~112%) and in some cases expanded by over >400% cover, depending on type of transplant material, planting arrangement and site. Higher bioturbator pressure from sandprawns (Kraussillichirus kraussi) significantly reduced transplant survival and area cover. Transplant plots were colonised by invertebrates, including seagrass specialists, such as South Africa's most endangered marine invertebrate, the false-eelgrass limpet (Siphonaria compressa). For future seagrass restoration projects, transplanting cores was deemed the best method, showing higher long-term persistence and cover, however this approach is also resource intensive with potentially negative impacts on donor meadows at larger scales. There is a clear need for further research to address Z. capensis restoration scalability and improve long-term transplant persistence.

Keywords: Climate change; Coastal ecosystems; Ecological interactions; Restoration; Seagrass conservation; Zostera capensis.

MeSH terms

Ecosystem*
South Africa
Zosteraceae*

Grants and funding

This research work was supported by funding from the National Research Foundation (NRF) through the Marine and Coastal Research funding instrument (Grant Number 116048). Katie M. Watson was supported through a grant-holder linked doctoral NRF bursary and a scholarship granted by Stellenbosch University’s Faculty of Science, Department of Botany and Zoology, and Sophie von der Heyden. The publication fee for this article was supported by IABO Members through the IABO Hub Cooperative Publishing Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.