The complexity of ecological impacts induced by great cormorants

Abstract

Following decades of global extermination, the general population of the great cormorant (Phalacrocorax carbo L.) is on the rise. The lack of regular predators, highly skilled fish rapacity, rapid metabolism, significant rate of excretion and ability to form large nesting colonies on relatively small areas lead to numerous environmental consequences of cormorant presence. Here we comprehensively review the occurrence and distribution of this species and, in particular, its multi-faceted impact on terrestrial and aquatic ecosystems and the main routes through which these impacts are being manifested. The bird-induced chemical loading and its biological and ecological consequences, and the effects on microbial pollution and pathogen dispersion are discussed in particular. The need for further investigation to fully elucidate particular effects is stressed throughout the paper. It is concluded that the environmental effects of great cormorants are rather complex, can lead to serious ecosystem modifications and that the presence of these birds should be taken into consideration in ecological assessment and monitoring.

Expansion of great cormorant colony immediately increased isotopic enrichment in small mammals

“…Investigations of the influence of great cormorant colonies have recently received more attention (see Ishida, 1996;Goc et al, 2005;Kameda et al, 2006;Nakamura et al, 2010;Klimaszyk et al, 2015;Klimaszyk and Rzymski, 2016). However, the impact of such colonies on plant and animal species is insufficiently investigated (see Bostrom et al, 2012;Kolb et al, 2012).…”

“…Cormorant excreta change soil pH, N and P levels and damage vegetation (Kameda et al, 2006;Klimaszyk and Rzymski, 2016), decreasing diversity of plants (Boutin et al, 2011), and affecting seed germination (Žółkoś and Meissner, 2008). Cormorant faeces may cover up to 5 80% of vegetation, with as many as 70 % of plant species disappearing in the established colonies, the rest being dominated by nitrophilous plants, such as elder (Sambucus nigra), common nettle (Urtica dioica), woodland groundsel (Senecio sylvaticus) and greater celandine (Chelidonium majus) (Goc et al, 2005;Klimaszyk et al, 2015).…”

Screening of protozoan and microsporidian parasites in feces of great cormorant (Phalacrocorax carbo)

“…Some studies also addressed the role of these birds in dispersion of bacterial pathogens such as Escherichia coli (Klimaszyk 2012; Klimaszyk and Rzymski 2013a, 2016), avian influenza virus (Albini et al 2014), avian paramyxovirus (Schelling et al 1999), and West Nile virus (Iashkulov et al 2008; Table 1). Recent studies also investigated the presence of gastric nematodes in these birds (Dziekońska-Rynko and Rokicki 2008; El-Dakhly et al 2012).…”

Short‐term Effects of Great Cormorant Droppings on Water Quality and Microbial Community of an Artificial Agricultural Reservoir

“…The great cormorant ( Phalacrocorax carbo ) is a waterbird found on every continent except South America and Antarctica. Information on this species is described in detail by Klimaszyk and Rzymski (2016). Briefly, great cormorants are piscivorous central‐place foragers (distance 10–15 km) composed of six subspecies.…”

“…Cormorants like to form colonies near bodies of water that are distant from human interference. Their numbers declined in the 1970s as a result of anthropogenic influences; cormorant populations have recovered over the past half century due to protection efforts, favorable feeding conditions, and their adaptation to climate change (Møller et al, 2008; Klimaszyk and Rzymski, 2016). In Japan, great cormorant numbers have significantly increased from 3000 pairs in the 1970s to >100,000 pairs in 2010 (Kameda and Tsuboi, 2013).…”