Page 6 - DeidunSchembri2006
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360 A. D EIDUN, P.J. SCH EMBRI
SIMPER showed that the observed differences between collections from Xatt 1-
Ahmar and Ramla, and the other beaches, could be attributed to the presence or
absence of just a few species. Six species account for about 66% of the dissimi-
larity between the Xatt l-Ahmar autumn and winter collections and most of the
remaining beach collections; thus, the fish Labrus sp. and Atherina sp. were mainly
present at Xatt 1-Ahmar and absent from the other beaches, while the mysid Siri-
ella clausii, the amphipods Gammarus subtypicus and Atylus swammerdami, and
the isopod ldotea baltica, were all absent from Xatt 1-Ahmar and present on the
remaining beaches. In addition, seven out of the nine polychaete species were
only collected from Xatt 1-Ahmar or Ramla. Six species (3 mysids, 2 amphipods
and l isopod) also account for about 66% of the dissimilarity observed between
the Ramla and Xatt 1-Ahmar spring and summer collections and those of the
other beaches.
Handnets both years combined l
~~omt~+1 )
etnblanC« 014 Bray CU1is
stre=: 0.12 POM
Q 9E·3
o 3.6E-2
e 0 6.3E-2
0 9E-2
2
2
Fig. 4 - N MDS plot of abundance data based on the Bray-Curtis similarity measure for col-
lections from both years (ali seasons) fo r the Maltese beaches only, with POM content
of the water as overlay.
NMDS plot dei dati di abbondanza basati sulla misura della simi/arità di Bray -Curtis per
campionarnenti per ambedue gli anni considerati ( tutte le stagioni) solo per le spiagge ma/tesi,
sovrapposti al cont.enuto in POM delle acque.
Conclusions
Wave action determines energy flow in nearshore environments by distribut-
ing organic materia! along the coastline (McLachlan & Bate, 1984). A correla-
tion between biotic patterns and particulate organic matter (POM) content of the
water column and/or exposure to wave action might therefore expected, but only
a weak correlation with POM was found and none with exposure or any of the
other abiotic parameters measured in the present study.
Analysis of the total dataset showed the Xatt 1-Ahmar autumn and winter
samples (and to a lesser extent even the Ramla and Xatt 1-Ahmar spring and
summer samples) to be distinct from the rest (Fig. 3). This distinctiveness of the
