<p>Modern economic activities, like industry and
agriculture, as well as household activities, generate an important amount of
refuse. The way we collect, transport, and dispose it will determine the level
of environmental contamination. May animals exploit refuse as a food source (i.e.,
anthropogenic food subsidy) and gulls are the most important group. Refuse
subsidizes energetically gull populations, which impacts on their acquisition
and allocation of resources, as well as on the environment, with ecological and
evolutionary consequences are not well understood. In this dissertation we
evaluated potential impacts of refuse on gulls by doing a literature review as
well as empirical research on the Kelp Gull (<i>Larus dominicanus</i>) in the Rio de la Plata Estuary in South America.
Direct and indirect impacts of refuse on gull species and the
environment have been observed during the review process. We have detected positive
impacts of refuse on body size, chick growth, fecundity, reproductive success,
and population dynamics. However, negative impacts were also found focusing on
fecundity, reproductive success, and population dynamics. Indirect negative
impacts on other species, water bodies, and airport security were also found. Refuse
produces numerous impacts on gulls at the individual, population, and species
levels, with indirect negative consequences on ecosystems. There is a need to
reduce the access of gulls to sources of refuse to mitigate the existing and
potential conflicts with human activities and other species, especially those
that are threatened and endangered. During our empirical research we found that
refuse was ingested and assimilated by Kelp Gull chicks during the chick
rearing period and that the ecological
niche width increased with the age of the chick. We propose that parents incorporate isotopically unique food sources to nestling’s
diet during their growth, increasing isotopic diversity of nestlings. Additionally,
we found that refuse could affect foraging decisions of females during the
pre-incubation period, which could positively affect future fecundity and
negatively impact reproductive success. We found also that refuse consumption
on fecundity and reproductive success of gulls is generally studied at the
colony level, using conventional diet techniques, but not much has been done
using stable isotopes at the individual level, making comparisons among studies
and conclusions difficult to address. We encourage other researchers to
continue incorporating the isotopic ecology perspective to study the effect of
food subsidies on gulls. Additionally, we found that Kelp Gull on the coast of
the Rio de la Plata Estuary ingest plastic debris. We conclude that plastic
bags and plastic films might be the most important source of contaminants for
the Kelp Gull on the coast of the estuary. Main findings of this dissertation
suggests the need for an improvement of waste management practices and a
regulation of plastic production and use in Uruguay to reduce plastic ingestion
by gulls. Finally, next steps for research are provided in this important area
of environmental science and natural resource management.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7403657 |
| Date | 04 January 2019 |
| Creators | Cesar J. Lenzi (5929943) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/THE_IMPACT_OF_REFUSE_ON_THE_KELP_GULL_LARUS_DOMINICANUS_IN_THE_R_O_DE_LA_PLATA_ESTUARY_URUGUAY/7403657 |
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