Proceedings of the Second Mediterranean Symposium on Marine

Jonge et al., 2002). Nutrient concentrations in water alone are not indicative <strong>of</strong>
eutrophication status, especially in shallow ecosystems, since primary producers
assimilate <strong>the</strong> nutrients very efficiently and respond non-linearly and self-accelerating
when certain nutrient boundaries are crossed (Duarte, 1995). High organic content <strong>of</strong>
sediment, in addition, could be toxic to marine angiosperms. Eutrophication is better
indicated by its symptoms, which in <strong>the</strong> lagoons include shifts in species composition
from angiosperms to <strong>the</strong> dominance <strong>of</strong> opportunistic and <strong>of</strong>ten bloom forming
seaweeds (Harlin, 1995; Schramm and Nienhuis, 1996). This predictable successional
dynamic <strong>of</strong> macrophytes is induced also by o<strong>the</strong>r kinds <strong>of</strong> human disturbance, e.g.
bottom-trawling, overharvesting <strong>of</strong> grazers or predators and is in accordance to classical
<strong>the</strong>ory <strong>of</strong> r- and K-selection.
The use <strong>of</strong> benthic macrophytes as bioindicators <strong>of</strong> eutrophication and <strong>of</strong> water quality
in general, several concepts, and numerical techniques (indicator taxa, diversity and biotic
indices, multivariate tools) have been developed. Although composition analysis at
species level is <strong>of</strong>ten measured, a more predictive science might be achieved by using
appropriate functional classifications. They could reduce <strong>the</strong> apparent complexity <strong>of</strong>
ecological systems and allow comparisons between communities with little species
overlap. Fur<strong>the</strong>rmore, <strong>the</strong>y could help to develop user-friendly protocols and costeffective
monitoring systems.
The idea <strong>of</strong> defining plant types that are in some way related to ecosystem function is
not new. For seaweeds, Littler and Littler (1980) have proposed functional groups, that
irrespective <strong>of</strong> phylogeny, are similar in morphology and similar in <strong>the</strong>ir responses to
certain ecosystem functions, e.g. productivity, grazing. Orfanidis et al. (2001, 2003) have
included seagrasses in this form-function system and <strong>the</strong>n have used it to divide <strong>the</strong>
benthic macrophytes in two differently responding to environmental disturbance groups,
<strong>the</strong> late-successional (K-selection) and <strong>the</strong> opportunistic (r-selection). The result <strong>of</strong> this
approach, which explains general macrophyte patterns across a pollution gradient mainly
through <strong>the</strong>ir competitive abilities (Sommer and Worm, 2002), was <strong>the</strong> Ecological
evaluation-EEI index.
In this study we monitored <strong>the</strong> marine benthic macrophytes across an eutrophication
gradient <strong>of</strong> selected Eastern Macedonian & Thrace lagoons. The aims were (1) to select
reliably interpretable signals <strong>of</strong> macrophyte responses by critically comparing different
parameters <strong>of</strong> composition analysis, based at species- and functional group-level, and <strong>the</strong>
biotic index EEI, (2) to suggest user-friendly protocols for a cost-effective monitoring
program, e.g. WFD.
MATERIAL AND METHODS
Study area. The studied lagoons belong to <strong>the</strong> Nestos River and Vistonida estuarine
system catchments (Fig. 1). They are protected by Ramsar convention and were
suggested to be included in <strong>the</strong> European Natura 2000 network. Traditional fish
aquaculture (mesh frames, stationary entrapment system) is <strong>the</strong> main commercial use <strong>of</strong>
<strong>the</strong> lagoons. The main nutrient sources <strong>of</strong> <strong>the</strong> Nestos lagoons are agricultural run-<strong>of</strong>fs
ACTES DU DEUXIEME SYMPOSIUM MEDITERRANEEN SUR LA VEGETATION MARINE (ATHENES, 12-13 DECEMBRE 2003)
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