A Review of Plastic-Associated Pressures: Cetaceans of the Mediterranean Sea and Eastern Australian Shearwaters as Case Studies

Abstract

Impacts of debris on marine fauna occur throughout the marine ecosystems, with adverse impacts documented on over 1,400 species; impacts can be divided into those arising from entanglement, and those from ingestion. Ingestion of, and entanglement in, debris has been documented in over 60% of all cetacean species. Seabirds are also impacted by debris predominately through entanglement and ingestion, with the number of species negatively impacted increasing from 138 to 174 over the past two decades. In the marine environment, cetaceans and seabirds are widely regarded as reliable sentinels due to their position near the top of the marine food web, conspicuous nature, and reliance on marine resources; for this reason, this paper is focused on seabirds and cetaceans as sentinels of ocean change. In particular, two case studies are considered in relation to different levels of environmental anthropogenic impact: the cetaceans of the Mediterranean Sea and seabirds of eastern Australia. Here we describe two recent studies used to diagnose the toxicological stress related to debris-associated pressures in cetaceans and seabirds. These studies highlight the diversity and scale of impacts being felt by marine species and the role these organisms can play in our society as charismatic sentinels of ocean health. Seabirds and marine mammals are exposed, in these key areas, to a variety of adversities that potentially decrease their survival or reproductive success. These include weather, food shortages, predators, competitors, parasites, disease, and human-induced effects and plastic pollution. Each factor affects seabirds and marine mammals in a different way, but more importantly, factors can also interact and create impacts far greater than any one factor alone. The Australian and Mediterranean case studies presented here emphasize the need to consider multiple sources of mortality when developing management plans for the conservation of vulnerable species.

Challenges for Sustained Observing and Forecasting Systems in the Mediterranean Sea

“…Information is still limited but Eriksen et al (2014) estimated floating plastic debris in the Mediterranean as 23,150 tons, with 3,056 corresponding to micro-and nanoplastics, which mirrors the 1,500 tons estimated from samples obtained by Ruiz-Orejón et al (2016). Biodiversity is highly affected by marine litter, either through entanglement, ingestion or colonization (Deudero and Alomar, 2015;Fossi et al, 2018). There is even a certain overlap between the feeding areas of diverse marine species and the convergence zones of floating microplastics (Fossi et al, 2017).…”

Tools and constraints in monitoring interactions between marine litter and megafauna: Insights from case studies around the world

“…pathology, mortality) and indirect (i.e. physiological, ecotoxicological) impact of interactions between these taxa and marine litter Werner et al, 2016 ;Fossi et al, 2018a;2018b;.…”

“…The primary impacts include ingestion and entanglement (Butterworth et al, 2012;Gregory, 2009;Kühn et al, 2015 though there is increasing concern about chemical contamination via ingestion (e.g. Fossi et al 2018a).…”

“…Despite an increase in the number of studies in recent years, information on marine debris ingestion in Mediterranean organisms remains very poor and inconsistent (Fossi et al 2018a;2018b). It is difficult to compare among different species and studies on amounts and types of ingested debris because data are not standardized.…”

Spatial Habitat Shifts of Oceanic Cephalopod (Ommastrephes bartramii) in Oscillating Climate

“…As cephalopods are generally short-lived taxa, they are known to swiftly respond to drastic climate and environmental perturbations, thus, making them effective biological sentinel of climatic changes [17,18]. In light of the rapidly changing climate, sentinel species can provide valuable information on ecosystem function, distinguish ocean and human health-related risks and forecast future changes [19][20][21]. Taking these characteristics into account and building upon the results of our foregoing work [6,22,23], we hereby extended our present analyses of squid-environment interactions to implement a simple yet ecologically pertinent approach to quantify the changes in potential squid habitat in the North Pacific under the recent thermal regimes, marked by distinct phase transitions of the Pacific decadal oscillation (PDO) between 1999 and 2013.…”