The results of the macroinfaunal communities distributions from the annual series surveys PORCUPINE are shown. Those surveys were realized during the months of September and October in the years 2006, 2008, 2009, 2010, 2011, 2012 and 2013 by the Instituto Español de Oceanografía aboard the R /V Vizconde de Eza, within the research project ERDEM. This survey series has as main objective the obtainment of abundance indexes of the benthonic and demersal fauna from Porcupine Bank, west of Ireland, with special attention on the commercial species exploited by the Spanish fleet (hake, angler fish, megrim and norwegian lobster).
For the study of the infaunal macrobenthos a total of 50 samples were analyzed from selected places of the Bank, where the bottom characteristics, the climatology or the survey schedule allowed. Samples were taken with an ULSNER box corer with 0.09 m2 of sampling area. Samples for the faunal study were sieved aboard with a 0.5 mm mesh size sieve. The material collected in the sieve was preserved with 8 % formaldehyde neutralized with borax, and stained with Rose Bengal solution for the posterior sorting and identification of fauna. Additional samples were taken to estimate the organic content of the sediment and to perform the granulometric analyses. Once in the laboratory, the granulometry was analyzed following the method recommended by Buchanan (1984); which consists in a combination of dry sieving of the coarse fraction (> 62 µm) and the sedimentation at 20 ºC of the fine fraction (< 62 µm) in a distilled water column. Sediment organic matter content was calculated as the percentage of weight loss by means of 24 hours sample calcination at 500 ºC, after dried it at 100 ºC during the same time. Complementary, in order to obtain a better coverage of the sedimentary types from the study area, more than 350 samples were collected with a net collector coupled to the trawling fishing gear (Baca-GAV 39/52).
Globally, the sediments of the majority of the sampled stations are mainly formed by sand, between fine and very fine, except in deep areas of the southeast, where there are large muddy areas with elevated organic content and high selection coefficient. In the north, around the shallowest area, we found thicker sandy sediments, with lower organic content and moderate selection.
The macroinfaunal communities from the Porcupine Bank are characterized by the dominance of the faunistic group of polychaetes (68.8 %), mainly represented by the families Owenidae, Spionidae, Paraonidae and Sabellidae. The next in number are the group of molluscs (17.6 %), dominated by the family Kelliellidae, which reaches maximum abundances up to 7520 ind•m-2. The poorest represented groups are the crustaceans (5.0 %), echinoderms (4.3 %) and the “others” (sipunculids, nemertine, etc.), being the latter the least abundant (3.7 %).
In relation with the spatial distribution four macroinfaunal groups were indentified in the Porcupine Bank:
- Group 1: located in intermediate depth areas, over sandy sediments with low organic content. The infaunal community is dominated by polychaetes from the Owenidae family, mainly represented by the specie Galathowenia oculata.
- Group 2: occupies the sandy and low organic content sediments from the shallowest area of the Bank. Polychaetes are the most representative faunistic group, highlighting the dominance of the families Spionidae and Paraonidae. Prionospio fallax and Aricidea wassi are the most representative species of the group.
- Group 3: situated in two deep areas in the south area of the Bank with muddy and high organic matter content sediments. It has the lowest infaunal abundance of the study, being dominated by the bivalve molluscs from the family Kelliellidae and by the annelids polychaetes from the family Paraonidae.
- Group 4: Is the cluster that includes more stations in throughout the study. It is distributed spatially in the south area of the Bank, in different bathymetries, with the most heterogeneous sediments and moderate organic content. The bivalve molluscs from the Kelliellidae family again become dominant, with Kelliella miliaris reaching abundance over 7500 ind•m-2.IE
