A Multi-Species Investigation of Sponges' Filtering Activity towards Marine Microalgae.

Despoina Varamogianni-Mamatsi,Manolis Mandalakis,Thekla I Anastasiou,Nicolas Kalogerakis,Nikos Papandroulakis,Thanos Dailianis,Emmanouela Vernadou

doi:10.3390/md20010024

Despoina Varamogianni-Mamatsi, Manolis Mandalakis + Show 5 more

Open Access

https://doi.org/10.3390/md20010024

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Abstract

Chronic discharge of surplus organic matter is a typical side effect of fish aquaculture, occasionally leading to coastal eutrophication and excessive phytoplankton growth. Owing to their innate filter-feeding capacity, marine sponges could mitigate environmental impact under integrated multitrophic aquaculture (IMTA) scenarios. Herein, we investigated the clearance capacity of four ubiquitous Mediterranean sponges (Agelas oroides, Axinella cannabina, Chondrosia reniformis and Sarcotragus foetidus) against three microalgal substrates with different size/motility characteristics: the nanophytoplankton Nannochloropsis sp. (~3.2 μm, nonmotile) and Isochrysis sp. (~3.8 μm, motile), as well as the diatom Phaeodactylum tricornutum (~21.7 μm, nonmotile). In vitro cleaning experiments were conducted using sponge explants in 1 L of natural seawater and applying different microalgal cell concentrations under light/dark conditions. The investigated sponges exhibited a wide range of retention efficiencies for the different phytoplankton cells, with the lowest average values found for A. cannabina (37%) and the highest for A. oroides (70%). The latter could filter up to 14.1 mL seawater per hour and gram of sponge wet weight, by retaining 100% of Isochrysis at a density of 105 cells mL−1, under darkness. Our results highlight differences in filtering capacity among sponge species and preferences for microalgal substrates with distinct size and motility traits.

Highlights

With the gradual increase of global population, and of fish food demand, the aquaculture industry has rapidly expanded over the last few decades [1]
We investigate the inherent filtering capacity and selectivity of four Mediterranean marine demosponges thriving in Greek waters, namely Agelas oroides, Axinella cannabina, Chondrosia reniformis and Sarcotragus foetidus, against three representative marine microalgae species of different size and motility characteristics: Nannochloropsis sp., Isochrysis sp. and Phaeodactylum tricornutum
Four Mediterranean sponge species were examined for their filtering activity: (a) Agelas oroides, (b) Axinella cannabina, (c) Chondrosia reniformis, and (d) Sarcotragus foetidus

Summary

Introduction

With the gradual increase of global population, and of fish food demand, the aquaculture industry has rapidly expanded over the last few decades [1]. High organic and nutrient loadings, generated from aquaculture activities (e.g., feed wastage, fish excretion, and fecal production), are continuously being released into the seawater [2], occasionally causing detrimental effects in the surrounding environment, such as toxic algal blooms, eutrophication and anoxia [3]. Such effects are likely at aquaculture settings located in sheltered areas such as gulfs and bays [4]. By offering several valorization opportunities, cultivation of sponges can become an extra source of profit for fish farmers and, their inclusion in IMTA systems is rather tempting

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