16
R. L. Fletcher
sewage outfalls include Phyllospadix torreyi in California (Littler and
Murray 1975), Posidonia oceanica in Egypt (Nasr and Aleem 1948), P.
oceanica in southeast Spain (Ruiz et al. 1990) and Zostera muelleri in
Tasmania (Buttermore 1977). The loss of these perennial macro algae and
phanero gams is particularly detrimental to the local ecology of the waters
as they provide a stable environment and invariably support a wide variety
of associated marine benthic plant and animal communities (collectively
called Cystoseira and seagrass associations respectively). The loss of these
associations can be particularly damaging to local fisheries as they frequently
act as nursery grounds for small fish; indeed, it is pertinent here to point out
that increased interest is being shown in the artificial establishment of
seaweed beds to enhance local fisheries in Japan (Largo and Ohno 1993).
Although the loss of these communities of large macro algae and seagrasses in eutrophicated waters can frequently be attributed to secondary
pollutants, e.g. suspended particulate material, toxic ingredients etc. (see
above), a number of reports have suggested that they are ousted by algae
more readily adaptable to the high nutrient loadings. Some examples of
sewage related floristic changes include those ofSfriso (1987), who reported
a decline/disappearance of a number of algae belonging to the Cystoseira
association in the Venice Lagoon, including the brown algae Dictyopteris
membranacea, Cladostephus verticillatus and T aonia atomaria and the red
genera Laurencia, Dasya and Polysiphonia, and their replacement by the
algae Dictyota dichotoma, Punctaria latifolia, Codium fragile, Ulva fasciata, Petalonia zosterifolia and Corallina officinalis. Munda (1974) reported the complete deterioration of the Fucus virsoides and Cystoseira spp.
associations (e.g. Cystoseira barbata) in the polluted waters of the northern
Adriatic around Rovinj and their replacement by a prolific growth of
Halopteris scoparia along with Ulva lactuca and Codium tomentosum.
Littler and Murray (1974, 1975) reported an increase in the mean algal cover
of Gelidium pusillum in an intertidal community near a sewage outfall on
San Clemente Island, California, whilst McNulty (1959) reported Gracilaria
blodgetti and Agardhiella tenera to be common inhabitants of sewage
outfall areas in Biscayne Bay, Florida. An increase in the cover of Gelidium
pusillum near a sewage outfall was also reported by Murray and Littler
(1974) on San Clemente Island, along with blue-green algae, Ulva
californica, Pterocladia capillacea and Petalonia fascia; this community replaced the more macroscopic and less pollution tolerant communities of Egregia laevigata subsp. borealis, Halidrys dioica, Sargassum
agardhianum, the sea grass Phyllospadix torreyi and a number of smaller
associated algae such as Gigartina canaliculata, Gelidium robistum and the
coralline alga Lithophyllum decipiens. Gamulin-Bridaet al. (1967), working
in the Bay ofN aples, also reported a reduction in the number of species with
R. L. Fletcher
sewage outfalls include Phyllospadix torreyi in California (Littler and
Murray 1975), Posidonia oceanica in Egypt (Nasr and Aleem 1948), P.
oceanica in southeast Spain (Ruiz et al. 1990) and Zostera muelleri in
Tasmania (Buttermore 1977). The loss of these perennial macro algae and
phanero gams is particularly detrimental to the local ecology of the waters
as they provide a stable environment and invariably support a wide variety
of associated marine benthic plant and animal communities (collectively
called Cystoseira and seagrass associations respectively). The loss of these
associations can be particularly damaging to local fisheries as they frequently
act as nursery grounds for small fish; indeed, it is pertinent here to point out
that increased interest is being shown in the artificial establishment of
seaweed beds to enhance local fisheries in Japan (Largo and Ohno 1993).
Although the loss of these communities of large macro algae and seagrasses in eutrophicated waters can frequently be attributed to secondary
pollutants, e.g. suspended particulate material, toxic ingredients etc. (see
above), a number of reports have suggested that they are ousted by algae
more readily adaptable to the high nutrient loadings. Some examples of
sewage related floristic changes include those ofSfriso (1987), who reported
a decline/disappearance of a number of algae belonging to the Cystoseira
association in the Venice Lagoon, including the brown algae Dictyopteris
membranacea, Cladostephus verticillatus and T aonia atomaria and the red
genera Laurencia, Dasya and Polysiphonia, and their replacement by the
algae Dictyota dichotoma, Punctaria latifolia, Codium fragile, Ulva fasciata, Petalonia zosterifolia and Corallina officinalis. Munda (1974) reported the complete deterioration of the Fucus virsoides and Cystoseira spp.
associations (e.g. Cystoseira barbata) in the polluted waters of the northern
Adriatic around Rovinj and their replacement by a prolific growth of
Halopteris scoparia along with Ulva lactuca and Codium tomentosum.
Littler and Murray (1974, 1975) reported an increase in the mean algal cover
of Gelidium pusillum in an intertidal community near a sewage outfall on
San Clemente Island, California, whilst McNulty (1959) reported Gracilaria
blodgetti and Agardhiella tenera to be common inhabitants of sewage
outfall areas in Biscayne Bay, Florida. An increase in the cover of Gelidium
pusillum near a sewage outfall was also reported by Murray and Littler
(1974) on San Clemente Island, along with blue-green algae, Ulva
californica, Pterocladia capillacea and Petalonia fascia; this community replaced the more macroscopic and less pollution tolerant communities of Egregia laevigata subsp. borealis, Halidrys dioica, Sargassum
agardhianum, the sea grass Phyllospadix torreyi and a number of smaller
associated algae such as Gigartina canaliculata, Gelidium robistum and the
coralline alga Lithophyllum decipiens. Gamulin-Bridaet al. (1967), working
in the Bay ofN aples, also reported a reduction in the number of species with