Intertidal and shallow subtidal sites on shores affected by oil in San Cristóbal
and Santa Fé Islands had been sampled prior to the oil spill. These data were
compared with data collected at the same sites 1 month later and at reference
locations that had not received oil. No clear effects of oil were detected, indicating
that impacts on shore communities of seaweeds, marine invertebrates and fishes
were probably slight. Increases in the density of several algal, sea urchin, hydroid
and fish taxa were detected adjacent to the wreck, and were probably caused by oil
pollution related to the Jessica spill (Edgar et al. 2002a).
The greatest oil pollution of shoreline contamination occurred on Floreana and
Isabela Islands. Lower levels of oil pollution were found at Santa Fé, Santa Cruz,
and San Cristóbal Islands and secondary contamination (oiled debris and foam)
was found on Española and Fernandina Islands. Only one survey site contained
sufficient coverage of oil to be termed ‘‘moderate’’. All other sites had ‘‘light’’ or
‘‘very light’’ surface oil (Lougheed et al. 2002).
Along the coast of mainland Ecuador, the absence of historical baseline data for
the invertebrate community is a real problem for determining impacts of this kind
of event on invertebrates.
Fishing has indirect effects on ecosystems, particularly through trophic cascades (Sala et al. 1998; Pinnegar et al. 2000; Jackson et al. 2001; Bascompte et al.
2005), in which sea urchins are important grazers. For instance, because sea
urchins can structure reef communities (Schiel and Foster 1986; Hughes et al.
1987; Pearse and Hines 1987), the removal of sea urchin predators (large lobsters
and fish) by artisanal fishing can increase the abundance of sea urchins. They can
then overgraze algae (Tegner and Dayton 1981; Tegner and Levin 1983; Siversten
2006). Overgrazing probably magnified impacts of the El Niño 1982–1983 through
a cascade of indirect effects involving population expansion of populations of
grazing sea urchins.
Edgar et al. (2010) indicated that shallow reef habitats across the central
Galápagos Archipelago underwent major transformation at the time of the severe
El Niño 1982–1983 warming event with consequences that persist today (BenstedSmith 2002). Heavily grazed reefs with crustose coralline algae (urchin barrens)
replaced former macroalgal and coral habitats, resulting in large local and regional
declines in biodiversity. Also, the range of corals decreased. Their ranges and their
populations are now largely confined to localized areas in the west (Glynn 1994)
and the north of the archipelago (Banks et al. 2009). One echinoderm, the 24-rayed
sunstar Heliaster solaris, has not been sighted since 1983 (Cairns 1991; Hickman
1998; Edgar et al. 2010). It is considered probably extinct in coastal environments
in Galápagos as probably extinct, because it has not been seen for [28 years (Red
List IUCN 2008). Marine protected areas with adequate enforcement are predicted
to ameliorate but not eliminate ecosystem impacts caused by increasing thermal
anomalies associated with El Niño and global climate change (Robinson 1985;
Edgar et al. 2010).
220
J. Sonnenholzner et al.
and Santa Fé Islands had been sampled prior to the oil spill. These data were
compared with data collected at the same sites 1 month later and at reference
locations that had not received oil. No clear effects of oil were detected, indicating
that impacts on shore communities of seaweeds, marine invertebrates and fishes
were probably slight. Increases in the density of several algal, sea urchin, hydroid
and fish taxa were detected adjacent to the wreck, and were probably caused by oil
pollution related to the Jessica spill (Edgar et al. 2002a).
The greatest oil pollution of shoreline contamination occurred on Floreana and
Isabela Islands. Lower levels of oil pollution were found at Santa Fé, Santa Cruz,
and San Cristóbal Islands and secondary contamination (oiled debris and foam)
was found on Española and Fernandina Islands. Only one survey site contained
sufficient coverage of oil to be termed ‘‘moderate’’. All other sites had ‘‘light’’ or
‘‘very light’’ surface oil (Lougheed et al. 2002).
Along the coast of mainland Ecuador, the absence of historical baseline data for
the invertebrate community is a real problem for determining impacts of this kind
of event on invertebrates.
Fishing has indirect effects on ecosystems, particularly through trophic cascades (Sala et al. 1998; Pinnegar et al. 2000; Jackson et al. 2001; Bascompte et al.
2005), in which sea urchins are important grazers. For instance, because sea
urchins can structure reef communities (Schiel and Foster 1986; Hughes et al.
1987; Pearse and Hines 1987), the removal of sea urchin predators (large lobsters
and fish) by artisanal fishing can increase the abundance of sea urchins. They can
then overgraze algae (Tegner and Dayton 1981; Tegner and Levin 1983; Siversten
2006). Overgrazing probably magnified impacts of the El Niño 1982–1983 through
a cascade of indirect effects involving population expansion of populations of
grazing sea urchins.
Edgar et al. (2010) indicated that shallow reef habitats across the central
Galápagos Archipelago underwent major transformation at the time of the severe
El Niño 1982–1983 warming event with consequences that persist today (BenstedSmith 2002). Heavily grazed reefs with crustose coralline algae (urchin barrens)
replaced former macroalgal and coral habitats, resulting in large local and regional
declines in biodiversity. Also, the range of corals decreased. Their ranges and their
populations are now largely confined to localized areas in the west (Glynn 1994)
and the north of the archipelago (Banks et al. 2009). One echinoderm, the 24-rayed
sunstar Heliaster solaris, has not been sighted since 1983 (Cairns 1991; Hickman
1998; Edgar et al. 2010). It is considered probably extinct in coastal environments
in Galápagos as probably extinct, because it has not been seen for [28 years (Red
List IUCN 2008). Marine protected areas with adequate enforcement are predicted
to ameliorate but not eliminate ecosystem impacts caused by increasing thermal
anomalies associated with El Niño and global climate change (Robinson 1985;
Edgar et al. 2010).
220
J. Sonnenholzner et al.