G. Radach, QUANTIFICATION OF LONG-TERM CHANGES IN THE GERMAN BIGHT USING AN ECOLOGICAL DEVELOPMENT INDEX, ICES journal of marine science (Print), 55(4), 1998, pp. 587-599
During recent decades, remarkable long-term changes have taken place i
n many coastal ecosystems of north-west European shelf seas. These cha
nges have been described in many papers, but an overall quantification
is lacking. An ecological development index (EDI) is proposed here, c
onsisting of two parts - a statistical description of the state of the
ecosystem and a metric in a multi-dimensional space of statistical de
scriptors of states for quantitatively characterizing the change of an
y number of state variables by only one characteristic number. The con
cept of the EDI is generally applicable by yielding a measure of the d
istance between system states. Indices are comparable between differen
t ecosystems and within different subspaces of the ecosystem's state s
pace, provided the same characterization is used. The concept is appli
ed to the 32-year time series (1962-1993) of measurements of nine phys
ical (sea-surface temperature, salinity), chemical (phosphate, nitrate
, nitrite, ammonia, silicate), and biological (biomass of diatoms and
flagellates) state variables at Helgoland. The analysis of consecutive
5-year quantiles of monthly mean values, which are used as statistica
l descriptors, elucidates the long-term perturbations of the coastal m
arine system in the German Bight. It is shown that the states of the e
cosystem in the 1970s and 1980s have abandoned the region of the 1960s
, but are possibly returning in the 1990s to the situation of the 1970
s. (C) 1998 International Council for the Exploration of the Sea.