Experimental harvest in a tropical seagrass meadow leads to shift in associated benthic communities

Abstract

Seagrass meadows represent key ecosystems in coastal areas worldwide, hosting a great biodiversity of associated communities and thereby providing a large range of ecosystem services. In this study we present an experimental approach to investigate the effects of seagrass losses on related macrofauna assemblages. Over a three year period, seagrass canopies were removed in experimental plots and changes in epifauna, infauna and respective functional groups were recorded. The experimental removal of seagrass leaves resulted in a decline of 74% of overall macrofaunal abundance and the loss of several taxa. The immediate response of associated communities was followed by the establishment of an alternative assemblage, characterized by an increased number of bioturbators and deposit feeders. The colonization of disturbed seagrass plots by burrowing shrimps (Callianassidae) might have hindered the reestablishment of seagrass after the removal. Our findings highlight the important role of seagrasses as habitat forming species that provide relevant functioning and services in coastal ecosystems.

Seagrass Loss and Sub-Surface Carbon Fate: Insights from a Long-Term Experimental Removal in Gazi Bay, Kenya

“…It has been hypothesized that significant changes to seagrass faunal communities may influence seagrass sediment carbon stocks, in particular bioturbators [11,12]. Burrowing shrimp of Gazi Bay, assumed to be part of the Callianassidae family, have an important bioturbation capacity, with a sediment turnover here estimated here to be around 948 ± 342 (SE)g.d -1 DW.…”

“…Seagrass loss can also lead to alterations in faunal communities with a shift toward a domination of bioturbator organisms, therefore accelerating the remineralisation of Corg [11,12]. In the sub-tropical and tropical regions of the world, the main macrofaunal bioturbators are Callianassidae shrimps (Decapoda : Axiidea) [13,14].…”

“…The study presented in this paper is a prolongation of this experiment, as the aim was to enhance our knowledge on the long-term effect of seagrass loss on sub-surface carbon stocks. It has been conducted in parallel with the seagrass macrofauna experiment presented in Cadier & Frouws [11]. While plots have been continuously harvested for 18 months preceding Githaiga sampling, they were left undisturbed until this sampling which happen 6 months after.…”

Climate change mitigation by coral reefs and seagrass beds at risk: How global change compromises coastal ecosystem services

“…Furthermore, an unstable sediment surface is likely to be uninhabitable for many currently existing benthic species within natural tropical bays, such as calcifying algae, urchins and juvenile lobster (Lozano-Álvarez et al, 2009). The benthic community has been shown to be tightly linked to the presence or absence of seagrass (Lundquist et al, 2018;Seitz and Ewers Lewis, 2018;Cadier and Frouws, 2019;Githaiga et al, 2019). Once seagrass is lost, the community assemblage often shifts toward bioturbating organisms that can further hinder seagrass reestablishment (Cadier and Frouws, 2019).…”

Pathways to link biodiversity and ecosystem functioning: from monitoring to complex ecological interactions studies

“…The loss of foundation species may increase the vulnerability of communities by triggering a sequence of extinctions (Berg et al 2015). Cadier and Frouws (2019) demonstrated that the removal of seagrass in Gazi Bay (Kenya) has negative impacts on associated benthic species that depended on this primary producer as habitat. The seagrass modifies the characteristics of the ecosystem by creating 3D structures above and below ground, increasing oxygenation of the sediment, increasing the trap of sediment and consequently carbon sequestration.…”