Dear List,

TO THE ATENTTION OF RESEARCHERS INTO MOLLUSCAN ECOLOGY.

I am a Spanish benthic ecologist, mainly a polychaetologist, working on
aspects of beta-diversity and the effect of impacts on macrobenthic
community structure.
I WOULD LIKE TO MAKE A PROPOSAL OF CO-AUTHORSHIP ON A PAPER ADDRESSING THE
EFFECT OF MACROALGAL MATS ON THE SPATIAL PATTERN OF MOLLUSCS FROM THE YTHAN
ESTUARY (EAST SCOTLAND).
        The target species for which abundances have allowed proper statistical
tretament are: Hydrobia ulvae, Mytilus edulis, Echinocardium edule and
Macoma balthica, any/all of them could be included in the paper.
        For those of you having an interest in this proposal look at the very
bottom of this messache where I have included the scientific rationale of
the project plus information on the study area and sampling approach. Dave
Raffaelli (Culterty Field Station, Aberdeen University, Scotland)
supervised the field work, and you can get any reference to my scientific
and personal profile profile (on request, I could also provide my CV).

WHY THIS PROPOSAL?
Thee years ago, I had to move away from my research base in the Canary
Islands (Spain) due to economical/job reasons, and I am presently living in
the Spanish Mediterranean coast where I work in forest surveillance. I do
not have bibliographic resources nor scientific expertise at hand to cope
with the elaboration of scientific publication, and I feel unable to devote
efforts to get those resources from abroad (In fact, I have done it for a
paper on Polychaete patterns from La Gomera Island (Canary Archipelago)
recently accepted by Cahiers de Biologie Marine and the struggle to get the
paper right wore me off).

ORIGIN OF THIS PIECE OF RESEARCH
This study wanted to be a training exercise leading to my PhD at the
Plymouth Marine Lab (England, UK) in which I designed a research program to
study the effect of anthropogenic stress on macrobenthic community
structure and its use as an impact assessment tool. My supervisor was to be
Mike Kendal who will so be happy to comment on any aspect of my project.
Unfortunately, such proposal was turned down by the European Community's
Research Committee under the Training and Movility of Researchers programme
(March 1998).

BASES OF COLABORATION
In writting the paper the kind of co-authorship I am rising is: I would
lead the methods and analysis sections, and I would expect the
colaborator/s to lead the introduction and discussion sections, parties
being keen about having and input in the each others' bit.

Looking forward to hearing from any of you.

SALVA


Salvador Herrando-Pérez
BSc, MPhil
C/ Padre Jofre 19, piso 3, pta 7
12006 Castellón de la Plana (Spain)
telephone 34 657787340
e-mail [log in to unmask]


1.- RATIONALE OF THE PROJECT

        Variability in patterns of faunal heterogeneity originate from natural or
anthropogenic disturbances of marine benthic communities (Warwick & Clarke
1993). The exact nature of these changes, their scale and the protocols for
sampling them have yet to be fully determined and require novel research if
they are to become useful as tools for detecting impacts. Caswell & Cohen
(1991) have modelled the hypothesis that increased levels of stress trigger
increased levels of community heterogeneity and their predictions tally
well with the observations of Warwick & Clarke (1993) on a number of
soft-bottom and coral-reef communities. Other authors who have worked on
the macrobenthos of submarine cliffs (Chapman et al. 1995), or on
soft-bottom nematodes from both abyssal and shallow waters (Lambshead &
Hodda 1994), have been unable to confirm the model’s validity. In all of
the latter accounts, statistical heterogeneity (pattern intensity), i.e.
testing for differences in measures of patchiness such as variance-to-mean
ratio (Elliot 1993) or index of multivariate dispersion (Warwick & Clarke
1993), or the graphical spread of (-diversity indexes, was used to assess
faunal hegerogeneity with no regard to the underlying geographical pattern
of the communities under study.
        The present investigation addresses the issue of faunal heterogeneity over
a perturbed macrobenthic community from the Ythan Estuary, UK. In the last
two decades, this estuary has experienced progressive eutrophication due to
run-off from agriculture and domestic sewage, and this has been coincident
with increases in green macroalgae biomass (Enteromorpha, Ulva and
Chaetomorfa spp.) by a factor of 3, up to above 1 kg.m-2 profusely
carpeting over 30-40 % of the mudflat area (Gorman & Raffaelli 1993;
Raffaelli & Way 1997). Macroalgae cause anoxic conditions in sediments
favouring epifaunal invertebrates but impoverishing very heavily the
infauna, with only certain tolerant species; whereas the magnitude of these
changes has a strong effect on food-web dynamics and stability, especially
on the population of shorebirds and fish feeding upon benthic invertebrates
(Nichols et al. 1981; Soulsby et al. 1982; Hull 1987; Raffaelli et al.
1989, 1991; Everett 1994; Norkko & Bonsdorff 1996; Raffaelli et al. 1997).
Thus, in the Ythan, weed-free patches of sediment act as a refuge for key
secondary producers such as the amphipod Corophium volutator, which can
colonise weed-affected areas once the algal break-down in Autumn (Raffaelli
et al. 1989). It is this spatial heterogeneity and temporal fluctuation
which may serve to maintain the food supply to higher trophic levels.
        Natural muddy sediments of the Ythan Estuary (UK) were contrasted against
areas impacted by extensive mats of green macroalgae for differences in
macrobenthic community structure and heterogeneity, three main topics being
dealt with:
I test the hypothesis that macroalgae mats, as a source of stress, will
cause increased levels of statistical heterogeneity in mollusc populations
(variance to mean ratios, .
Pattern intensity does not necessarily imply spatial heterogeneity within a
geographic pattern (pattern form) (Sokal 1978). Thus, I also examine
macrobenthic spatial patterns in order to understand how stress can control
multivariate species distributions. This is accounted for by spatial
correlograms as described by Sokal (Sokal & Oden 1978a; 1978b; Thrush 1990).


2.- STUDY AREA AND SAMPLING APPROACH
        The study area was located in the northern mudflats of the Quay (Ythan
Estuary, Sands of Forvie NNR, Scotland, UK), in front of the Culterty Field
Station (Fig. 1). Areas free of and blanketed with green macroalgae could
be there easily selected for comparative study.
        A total of three 91x91 cm2 plots, 10-15 m. apart, were located in both
unweeded and weeded areas. Sampling was undertaken with a 7 cm diameter
corer, pushed 6 cm into the sediment, a regime suitable for the local
macrobenthos (see Lawry 1997). Each plot consisted of a grid of 9
reticulated squares with 7 cm internode distance (Fig. 2). One sample was
withdrawn from the vertices of every square, while 3 further corers were
taken from 3 randomly selected nodes in each square (43 samples/plot). This
methodology ensured sample collection from the whole plot surface. Each
sample was given a position according to the cartesian space of the grid
(Fig. 2). Samples were labelled and collected in plastic bags and, back at
the lab, sieved. Macrofauna (>500 (m) was stored in formaline, and
subsequently identified to species level and counted, while the associated
macroalgae in the samples from the weeded plots was quantified by their wet
weight.