Effect of water clarity on the distribution of marine birds in nearshore waters of Monterey Bay, California

Abstract

The distribution of marine birds relative to water clarity was examined in the nearshore waters of Monterey Bay, California. I conducted nine at‐sea surveys in 1999 and 2000 and simultaneously recorded water clarity and the density of five taxa of marine birds. Among plunge‐divers, Forster's Terns (Sterna forsteri) occurred more frequently than expected over turbid water (<2.5 m Secchi depth) and, among pursuit‐diving species, Brandt's Cormorants (Phalacrocorax penicillatus) occurred most often in the clearest water available (>5 m Secchi depth). Turbidity in Monterey Bay may be caused by suspended organic matter, including phytoplankton, during summer and fall. Forster's Tern may prefer such areas because small fish are likely to occur near this potential food source. Brandt's Cormorants probably rely on vision to catch fish near the bottom and turbid water may reduce available light and limit visual acuity. The distribution of Brown Pelicans (Pelecanus occidentalis), Western/Clark's Grebes (Aechmophorus occidentalis/clarkii), and Marbled Murrelets (Brachyramphus marmoratus) did not appear to be influenced by turbidity levels, indicating that some seabirds use marine habitats with a wide range of water clarities.

Complexity of domoic acid-related sea lion strandings in Monterey Bay, California: foraging patterns, climate events, and toxic blooms

“…Similarly, more sea lions were observed during these time periods in the Bay than in other years (Goldstein et al 2008, Henkel & Harvey 2008. In 2000, coastal waters off the southern California region experienced weaker than normal upwelling and lower productivity, whereas production remained near normal in central and northern California (Durazo et al 2001, Henkel & Harvey 2008. Adult females (n = 10) stranded in larger than usual numbers in Monterey Bay.…”

“…CSL are one of the most abundant pinnipeds in the California Current System (Henkel & Harvey 2008 (Scholin et al 2000). Shaded areas show months in 1998, 2000 and 2007 when large numbers of CSL stranded with signs of acute DA poisoning with large annual breeding and foraging movements that differ by age and sex (Melin et al 2000).…”

“…However, most of the female sea lion population would have been expected to remain near the Channel Islands nursing their pups. With lowered productivity and decreased prey abundance further south, females were likely traveling northwards in greater numbers to forage (Henkel & Harvey 2008), resulting in exposure to high levels of DA and increased numbers of related strandings.…”

Visual prey availability and distribution of foraging little auks (Alle alle) in the shelf waters of West Spitsbergen

“…Visual range and resolution are poorer underwater than on land, and this limits the distance over which potential prey can be detected and makes feeding more difficult (Martin and Prince 2001). Water transparency is determined mainly by the amount of suspended inorganic and organic particles, including phytoplankton, and is of importance to diving seabirds, since an increase in turbidity reduces their visual acuity (Eriksson 1985;Aksnes and Giske 1993;Kuroki et al 2003;Henkel 2006). The optical properties of water and the abundance and vertical distribution of prey in the feeding grounds influence diving behaviour and foraging efficiency of different groups of seabirds, depending on the hunting technique they use (Ainley 1977).…”

Environmental Predictors of Seabird Wrecks in a Tropical Coastal Area

“…Cabot’s terns feed via surface plunging with limited access to fish below the water column [103] and, for this reason, exhibit narrower diet. Thus the species is more sensitive to declines in prey availability caused by increased water turbidity and adverse weather conditions, which disrupt surface foraging visibility [105]. …”