Environmental requirements for three sea pen species: relevance to distribution and conservation

Abstract

The aim is to determine the environmental requirements, estimate the extent of suitable habitat for three sea pen species, and assess the implications for marine protected areas (MPAs). The sea pen Funiculina quadrangularis and the habitat associated with two further sea pen species, Virgularia mirabilis and Pennatula phosphorea, are of key conservation importance and are recommended for protection within MPAs. This study models their potential distributions using the MAXimum ENTropy algorithm and assesses these in relation to five possible marine protected areas (pMPAs) proposed for Scottish waters. Metrics relevant to assessing the efficacy of MPAs are also presented. Four environmental variables of prime importance for predicting the presence of all three species of sea pen were identified: mud, minimum salinity, depth, and gravel. The habitat suitability index increased with mud content. The modelled distribution of F. quadrangularis indicated a deeper distribution than V. mirabilis or P. phosphorea and was not present in sediment with gravel content above 30%. Pennatula phosphorea had the smallest area of suitable habitat, while V. mirabilis had the largest. The percentage predicted suitable area for each species that was encompassed by the five pMPAs ranged from 11% for F. quadrangularis to 15% for P. phosphorea. Some of the largest areas predicted as suitable for F. quadrangularis lay outside the pMPAs. The model results indicated differences in the environmental requirements of the three species of sea pen that can be linked to the autecology of each species. Patch sizes, calculated from a binary output of the model, were used to estimate the degree of habitat fragmentation, thereby giving a partial assessment of the adequacy criterion for these pMPAs. The results suggest that potential MPAs within the study area cover sizeable areas of potential sea pen habitat. However, further areas suitable for F. quadrangularis could be considered.

A Comparison of Fishes and Invertebrates Living in the Vicinity of Energized and Unenergized Submarine Power Cables and Natural Sea Floor off Southern California, USA

“…For instance, several species of sea pens in Scottish marine waters are abundant in mud and become rare or, ultimately, absent as the amount of gravel increases [21]. As noted before, it is possible that currents, playing over the cables, can distribute sediments based on grain size, thus leading to coarser sediments on one side and finer ones on the other.…”

Cold Temperate Coral Habitats

“…Although the number of studies is limited, sea pens appear to have fewer associated organisms compared to scleractinians and gorgonians. Funiculina quadrangularis is a species with greatest conservation importance in the greater North Sea and Celtic Sea areas [78]. It can become a little more than 2 m tall, with approximately one quarter of the lower part of the structure embedded in the sediment [78].…”

“…Funiculina quadrangularis is a species with greatest conservation importance in the greater North Sea and Celtic Sea areas [78]. It can become a little more than 2 m tall, with approximately one quarter of the lower part of the structure embedded in the sediment [78]. Predators on sea pens include nudibranchs, which have been observed preying on sea pen polyps.…”

Sea pen (Pennatulacea) aggregations on the northern Spanish shelf: distribution and faunal assemblages

“…are known to be much stouter and fleshier than F. quadrangularis (Manuel 1981), which probably helps them to settle in less homogeneous sediments. In fact, both species are known to occur in muddy substrata, but Manuel (1981) also reported P. phosphorea in sandy substrata and Greathead et al (2015) reported the absence of F. quadrangularis in sediment with gravel content above 30%.…”