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VERTIMAR-2005
Symposium on Marine Accidental Oil Spills
Temporal evolution of infaunal and suprabenthic communities
on the Galician continental shelf (NW, Iberian Peninsula),
after the Prestige oil spill
Santiago PARRA and Inmaculada FRUTOS
Instituto Español de Oceanografía, C.O. de A Coruña, Apdo. 240, 15001 A Coruña, Spain
1. INTRODUCTION
In November, 2002 the single-hulled tanker Prestige sank 130 miles off the coast of Muxía
(A Coruña, Galicia). Roughly 20,000 tons of fuel oil spilled into the sea, causing a vast black
tide which mainly affected the entire Galician coast. During the 2002-2004 period a series of
oceanographic surveys were conducted using different, complementary sampling systems to be
able to quantify the different compartments of the bottom ecosystem (infauna, suprabenthos,
epifauna and megafauna) and to acquire knowledge on the state of the communities and
resources (Sánchez, 2003; Serrano et al., in press). A sampling strategy was designed to
include bottom stations located in two geographic sectors organized in a radial arrangement at
three depth strata. This paper presents new data on the temporal evolution of the sediment
characteristics in all the sectors and depth strata during the 2002-2004 period and temporal
changes in the infaunal communities (zones 1 and 2, depth strata A and B) and suprabenthic
communities (zone 3, depth strata A, B and C) during the first year of study (2002-2003).
2. RESULTS AND DISCUSSION
No important changes were seen in the temporal evolution of the sedimentological
characteristics (granulometry and organic content) of the stations under study during the entire
study period (2002-2004). As regards the infaunal communities zone 1, in stratum A (71-120
m), the stations presented mud bottoms or fine sands with a moderate amount of organic
content. The dominant zoological group in terms of abundance in this stratum were the
polychaetes (accounting for over 77 %), with the spionid Prionospio fallax being the
characteristic species. One of the outstanding traits of the temporal evolution in this depth
stratum was the increase in spring in the abundance of the polychaetes and molluscs and the
decreasing presence of the group “others”. In stratum B (121-200 m) the stations had a
sediment made up of fine sands with a low organic content. In this stratum, the polychaetes
were also the prevailing zoological group with the dominant species being Prionospio fallax,
Monticellina dorsobranchialis and Aricidea sp. As regards the temporal evolution in this depth
stratum, we may point to a slight decline in the abundance of polychaetes in spring and a
significant increase in molluscs and crustaceans, and to a lesser extent, the group “others”.
The stations located in the most shallow stratum (A; 71-120 m) of zone 2, presented mud
bottoms or fine sands with a moderate to low organic content. In this stratum the dominant
zoological group in abundance were the polychaetes (which did not exceed 70% of the
abundance), followed by the echinoderm, molluscs and “others”, accounting for over 10%. The
most common species were the polychaetes Prionospio fallax and Tharyx sp., the echinoderm
Amphiura filiformis and the bivalve Mysella bidentata. In the temporal evolution of these depth
strata we may highlight a decrease in the abundance of the polychaete group in spring and a
significant rise in the echinoderms and, to a lesser extent, in the groups molluscs, crustaceans
and “others”. The stations in stratum B (121-200 m) had a characteristic sediment comprised of
very fine sands with a moderately selected low organic content. The dominant zoological group
in this stratum was made up of the polychaetes (more than 73 %), followed by the crustaceans
which accounted for up to 12.73 %. The characteristic species in this stratum were the
peracarida crustacean Ampelisca sp. and the polychaetes Prionospio fallax, P. steentrupii and
Monticellina dorsobranchialis. The temporal evolution of this depth strata in spring exhibited a
slight increase in the abundance of the group molluscs and crustaceans and a decrease in the
group “others”. The dominant species, the polychaetes, did not undergo any significant
changes.
Overall, slight variations in the population parameters were seen in the winter and spring in
zone 1. The most significant changes in spring were a slight decrease in total abundance and in
VERTIMAR-2005
Symposium on Marine Accidental Oil Spills
the abundance of some of the less important groups while the crustaceans underwent a modest
increase, particularly in the deepest stratum (figure 1). Species richness, diversity and
equitableness rose slightly. The most notable decrease was found in total abundance and in the
group “others”, while increased values were recorded for molluscs, echinoderms and
crustaceans in spring. At present, no important changes were seen in the temporal evolution of
the bioindicator infaunal species (opportunistic or sensible oil spill species) during the first study
period (2002-2003), like was observed in 1993, in A Coruña coast, after Aegean Sea oil spill
(Gómez Gesteira and Dauvin, 2000; Parra and López-Jamar, 1997).
ZONE 1
WINTER
ZONE 2
SPRING
Total
WINTER
SPRING
Total
Stratum A
Stratum A
Stratum B
Stratum B
Polychaetes
Echinoderms
Others
Molluscs
Crustaceans
Figure 1: Percentage of total infaunal abundance shown by taxonomic group in zones 1 and 2,
by depth strata.
The suprabenthic communities under study from the shallowest stratum (71-120 m) of zone
3 were dominated by the amphipod Amphilochoides boecki, the mysids Leptomysis gracilis and
Anchialina agilis and the euphausiid Nyctiphanes couchi. As regards the temporal evolution, we
may point to an increase in spring in the abundance of the group euphausiids along with a
substantial decrease in the amphipods and mysids.
In the middle stratum (121-200 m) of zone 3, the community was characterised by the
mysids Anchialina agilis and Erythrops neapolitana and the euphausiid Nyctiphanes couchi. On
a temporal level, we observed a considerable increase in the amphipods in addition to a less
important decrease in the cumaceans and euphausiids in spring.
In contrast, in the deepest stratum (201-500 m) of zone 3, where the winter community was
dominated by the decapods, this group underwent a substantial decline accompanied by a great
rise in the euphausiids group. The dominant species in this community were the decapod
Pasiphaea sivado, the amphipods Scopelocheirus hopei and Orchomenella nana.
REFERENCES
Gómez Gesteira, J.L., Dauvin, J.-C., 2000. Amphipods are good bioindicators of the impact of
oil spills on soft-bottom macrobenthic communities. Mar. Poll. Bull. 40, 1017-1027.
Parra, S. y López-Jamar, E., 1997. Cambios en el ciclo temporal de algunas especies
endofaunales como consecuencia del vertido del petrolero Aegean Sea. Publ. Esp. Ins. Esp.
Oceanogr. 23, 71-82.
Sánchez, F., 2003. Presencia y cuantificación del fuel sedimentado en las plataformas de
Galicia
y
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Serrano, A., Sánchez, F., Preciado, I., Parra, S. and Frutos, I. In press. Spatial and temporal
changes in benthic and demersal communities of the Galician continental shelf after the
Prestige oil spill. Mar. Poll. Bull.