Community Composition and Habitat Characterization of a Rock Sponge Aggregation (Porifera, Corallistidae) in the Cantabrian Sea

Pilar Ríos,Francisca C Carvalho,Teodoro P Ibarrola,Francisco Sánchez,Elena Prado,Javier Cristobo,Joana R Xavier,Augusto Rodríguez-Basalo

doi:10.3389/fmars.2020.00578

Abstract

Deep-sea sponge-dominated communities are complex habitats considered hotspots of biodiversity and ecosystem functioning. They are classified as Vulnerable Marine Ecosystem and are listed as threatened or declining as a result of anthropogenic activities. Yet, studies into the distribution, community structure and composition of these habitats are scarce, hampering the development of appropriate management measures to ensure their conservation. In this study we describe a diverse benthic community, dominated by a lithistid sponge, found in two geomorphological features of important conservation status —Le Danois Bank and El Corbiro Canyon— of the Cantabrian Sea. Based on the analyses of visual transects using a photogrammetric towed vehicle and samples collected by rock dredge, we characterize the habitat and the associated community in detail. This deep-sea sponge aggregation was found on bedrock. It is dominated by one lithistid sponge, Neoschrammeniella aff. bowerbankii (0.2 ind./m2) and further composed of various sponge species as well as of other benthic invertebrates such as cnidarians, bryozoans and crustaceans. Using a non-invasive methodology(SfM - Structure from Motion) and empirical relationships of individuals size and biomass/volume obtained in laboratory for N. aff. bowerbankii, we were able to estimate a total biomass of 41 kg and volume of 39 l of this species in the surveyed area. This approach allows a fine tune methodology for estimating biomass and volume by image-based-observed area avoiding destructive techniques for this species.

Highlights

Sponges constitute an important component of the benthic marine communities, in deeper environments where they play fundamental ecological roles (Pomponi et al, 2019)
The main aim of this study was to (a) characterize and describe the habitat of a benthic community dominated by a lithistid sponge, and (b) establish morphometric relationships of this species to estimate population structure parameters from underwater imagery, in the Avilés Canyon System and Le Danois Bank
We report the discovery of a benthic community dominated by a lithistid sponge in two areas of the Cantabrian Sea, providing a characterization of this community and its habitat

Summary

Introduction

Sponges constitute an important component of the benthic marine communities, in deeper environments where they play fundamental ecological roles (Pomponi et al, 2019). Under particular ecological conditions sponges are able to form concentrations or beds of high abundances building habitats for other species and increasing the biodiversity with respect to surrounding areas, especially the associated fauna of other invertebrate and fish (Bett and Rice, 1992; Klitgaard, 1995; Kunzmann, 1996; Bo et al, 2012; Beazley et al, 2013; Fillinger et al, 2013) These evidences indicate that efforts to close areas dominated by deep-sea sponge aggregations to bottom-tending gears will serve to meet the conservation objectives of the UNGA Resolution 61/105, that drew attention to the importance of the benthic megafauna, in vulnerable marine ecosystems. This lack of knowledge is most evident in deep-sea species due to the complexity of their study

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