236
While the species-based indices are mainly designed for assessing the
water quality of a waterbody (e.g. pollution), the EBQI provides a picture
of the actual status of the ecosystem functioning, including not only pollution but also the whole range of human impacts, from anchoring to
overfi shing.
1
The Issue
Biotic indices are extensively used in the marine
realm (1) to assess the quality of a waterbody; (2)
to assess processes such as currents, sedimentation and climate under natural and anthropogenic
forcing; and (3) to monitor the status of species
or communities of interest, either emblematic
species, indicators of ecosystem health or indicators of pollution (e.g. Orfanidis et al. 2001 , 2003 ,
2011 ; Pergent-Martini et al. 2005 ). Sometimes,
species used as biological indicators are key species or ecosystem engineers. This is the case of
the seagrass Posidonia oceanica (Linnaeus)
Delile (Boudouresque et al. 2006 ; Romero et al.
2007 ; Gobert et al. 2009 ; Lopez y Royo et al.
2010 , 2011 ; Marbà et al. 2012 ).
However, does an indicator based on the
health of a species, or a few species, give information about the health of the entire ecosystem
to which it belongs? Here, we use a recently proposed ecosystem-based index of the P. oceanica
seagrass meadow (EBQI) and compare it with
species-based indices.
2
The Conceptual Model
and the EBQI
The seagrass Posidonia oceanica is endemic to
the Mediterranean Sea. It constitutes extensive
meadows between the mean sea level and down
to 30–40 m in depth (Molinier and Picard 1952 ;
Boudouresque and Meinesz 1982 ; Boudouresque
et al. 2009 , 2012 ; Pergent et al. 2012 ).
We used an updated version (Fig. 1 ; Ruitton
et al. 2013 ; Personnic et al. 2014 ) of the conceptual model of the functioning of the P. oceanic a
ecosystem proposed by Boudouresque et al.
( 2012 ). Interestingly, P. oceanica ecosystem
itself is closely coupled with the pelagic coastal
ecosystem (Plankton, POM, planktivorous teleosts) and more loosely coupled with terrestrial
ecosystems through seabirds (Morat et al. 2011 )
and dead P. oceanica leaves (Cardona et al.
2007 ).
The rationale governing the EBQI (EcosystemBased Quality Index) is (1) trying to quantify and
assess some compartments (boxes 1 through 13;
Fig. 1 ) of the conceptual model by means of a set
of parameters, (2) determining their relative
weight and (3) by using a simple algorithm, calculating a rank for the ecosystem status within a
given area, matching the fi ve classes of the ecological status of the European Union Water
Framework Directive (WFD) (Water Framework
Directive 2000 ), from bad to high (Ruitton et al.
2013 ; Personnic et al. 2014 ).
The status of each functional compartment
(box) was assessed by means of a semiquantitative scale (4 through 0), from very good
(4) to very bad (0). Calibration of the scale was
based upon the available literature (e.g. UNEPMAP- RAC/SPA 2011 ). Compartments were
weighted according to their relative importance
in the ecosystem functioning, from 5 (highest
weighting) to 1 (lowest weighting). The grade for
each compartment was given by its status (0
through 4), multiplied by its weighting (1 through
5) and was therefore graded from 0 to 4 and 0 to
20 (depending upon the weighting of the considered compartment). The grades of all compartments were added up, which gave the fi nal grade
of the ecosystem status (EBQI) at a given site.
For practical purposes, the EBQI was converted
to a scale from 0 to 10 (Table 1 ). The EBQI was
applied to 17 localities of the northwestern
Mediterranean, from the Balearic Islands to the
French Riviera and Corsica (Table 1 ; Personnic
et al. 2014 ).
C.F. Boudouresque et al.
While the species-based indices are mainly designed for assessing the
water quality of a waterbody (e.g. pollution), the EBQI provides a picture
of the actual status of the ecosystem functioning, including not only pollution but also the whole range of human impacts, from anchoring to
overfi shing.
1
The Issue
Biotic indices are extensively used in the marine
realm (1) to assess the quality of a waterbody; (2)
to assess processes such as currents, sedimentation and climate under natural and anthropogenic
forcing; and (3) to monitor the status of species
or communities of interest, either emblematic
species, indicators of ecosystem health or indicators of pollution (e.g. Orfanidis et al. 2001 , 2003 ,
2011 ; Pergent-Martini et al. 2005 ). Sometimes,
species used as biological indicators are key species or ecosystem engineers. This is the case of
the seagrass Posidonia oceanica (Linnaeus)
Delile (Boudouresque et al. 2006 ; Romero et al.
2007 ; Gobert et al. 2009 ; Lopez y Royo et al.
2010 , 2011 ; Marbà et al. 2012 ).
However, does an indicator based on the
health of a species, or a few species, give information about the health of the entire ecosystem
to which it belongs? Here, we use a recently proposed ecosystem-based index of the P. oceanica
seagrass meadow (EBQI) and compare it with
species-based indices.
2
The Conceptual Model
and the EBQI
The seagrass Posidonia oceanica is endemic to
the Mediterranean Sea. It constitutes extensive
meadows between the mean sea level and down
to 30–40 m in depth (Molinier and Picard 1952 ;
Boudouresque and Meinesz 1982 ; Boudouresque
et al. 2009 , 2012 ; Pergent et al. 2012 ).
We used an updated version (Fig. 1 ; Ruitton
et al. 2013 ; Personnic et al. 2014 ) of the conceptual model of the functioning of the P. oceanic a
ecosystem proposed by Boudouresque et al.
( 2012 ). Interestingly, P. oceanica ecosystem
itself is closely coupled with the pelagic coastal
ecosystem (Plankton, POM, planktivorous teleosts) and more loosely coupled with terrestrial
ecosystems through seabirds (Morat et al. 2011 )
and dead P. oceanica leaves (Cardona et al.
2007 ).
The rationale governing the EBQI (EcosystemBased Quality Index) is (1) trying to quantify and
assess some compartments (boxes 1 through 13;
Fig. 1 ) of the conceptual model by means of a set
of parameters, (2) determining their relative
weight and (3) by using a simple algorithm, calculating a rank for the ecosystem status within a
given area, matching the fi ve classes of the ecological status of the European Union Water
Framework Directive (WFD) (Water Framework
Directive 2000 ), from bad to high (Ruitton et al.
2013 ; Personnic et al. 2014 ).
The status of each functional compartment
(box) was assessed by means of a semiquantitative scale (4 through 0), from very good
(4) to very bad (0). Calibration of the scale was
based upon the available literature (e.g. UNEPMAP- RAC/SPA 2011 ). Compartments were
weighted according to their relative importance
in the ecosystem functioning, from 5 (highest
weighting) to 1 (lowest weighting). The grade for
each compartment was given by its status (0
through 4), multiplied by its weighting (1 through
5) and was therefore graded from 0 to 4 and 0 to
20 (depending upon the weighting of the considered compartment). The grades of all compartments were added up, which gave the fi nal grade
of the ecosystem status (EBQI) at a given site.
For practical purposes, the EBQI was converted
to a scale from 0 to 10 (Table 1 ). The EBQI was
applied to 17 localities of the northwestern
Mediterranean, from the Balearic Islands to the
French Riviera and Corsica (Table 1 ; Personnic
et al. 2014 ).
C.F. Boudouresque et al.