Abstract
Although the effect of ecosystem engineers in structuring communities is common in several systems, it is seldom as evident as in shallow marine soft-bottoms. These systems lack abiotic three-dimensional structures but host biogenic structures that play critical roles in controlling abiotic conditions and resources. Here I review how reef-building polychaetes (RBP) engineer their environment and affect habitat quality, thus regulating community structure, ecosystem functioning, and the provision of ecosystem services in shallow waters. The analysis focuses on different engineering mechanisms, such as hard substrate production, effects on hydrodynamics, and sediment transport, and impacts mediated by filter feeding and biodeposition. Finally, I deal with landscape-level topographic alteration by RBP. In conclusion, RBP have positive impacts on diversity and abundance of many species mediated by the structure of the reef. Additionally, by feeding on phytoplankton and decreasing water turbidity, RBP can control primary production, increase light penetration, and might alleviate the effects of eutrophication affecting supporting ecosystem services, such as nutrient cycling. They can also modulate cultural ecosystem services by affecting recreational activities (e.g., negative impacts on boating and angling, increased value of sites as birdwatching sites). Acknowledging the multiplicity of synergistic and antagonistic effects of RBP on ecosystems and linking changes in habitat structure, filter-feeding activities, and biodeposition to ecosystem services are essential for effective decision-making regarding their management and restoration.
Highlights
After some controversy [1,2], the term “ecosystem engineer” is widely accepted to denote the organisms that indirectly or directly modulate the availability of resources to other species via structural modifications of the environment [3]
I illustrate that the ecosystem engineering impact of reef-building polychaetes (RBP) can be extremely important for community structure and ecosystem functioning in these systems
This review focuses on the effects of filter-feeding polychaetes on physical structure and functions of shallow waters ecosystems and, on the impact of ecosystem engineering polychaetes that build reefs (Table 1)
Summary
After some controversy [1,2], the term “ecosystem engineer” is widely accepted to denote the organisms that indirectly or directly modulate the availability of resources to other species via structural modifications of the environment [3]. I illustrate that the ecosystem engineering impact of RBP can be extremely important for community structure and ecosystem functioning in these systems These structure-forming species affect soft-bottom environments and their inhabitants via several mechanisms, including the alteration of water flow and bed-load sediment transport [31], the accumulation of organic matter between reefs [32], and the formation of a complex hard substrate habitat [33]. The reefs themselves act as sediment traps ameliorating physical conditions by sediment accumulation and stabilization [34] Through these and other effects on the abiotic environment, RBP increase biotic diversity and abundance [26,35,36] and modify the distribution of infaunal and epifaunal organisms [37].
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