Bacteria control levels of dangerous pollutant in seabirds

Mercury levels in cormorants and petrels stable over past 50 years

Date: December 16, 2016

Source: McGill University

Researchers have discovered that levels of mercury in seabirds off the coast of British Columbia have remained relatively stable over the past 50 years. This might appear to be good news, but it is due to a decline in fish stocks near the surface which has forced seabirds to feed in areas where there are more bacteria (known as sulfate-reducing bacteria) which control the levels of mercury.

Although tiny, bacteria can be very important -- try to make yogurt or miso soup without them. Now, researchers at McGill University and Environment and Climate Change Canada have discovered that bacteria play an important role in determining the health of birds at the top of the food web. By using isotopic tracers called stable isotopes, researchers showed that seabirds feeding in areas rich in sulfate (a chemical that is an important food for sulfate-reducing bacteria that help break down organic matter) had high levels of mercury. Those same sulfate-rich areas were favoured by the sulfate-reducing bacteria which produce methylmercury, a toxic substance which is then taken in by the fish that eat them and eventually by the seabirds that feed on the fish.

The authors of a recent paper published in Environmental Science and Technology used seabird eggs collected along the Pacific coast of Canada over 47 years, and archived by Environment and Climate Change Canada in Ottawa. They documented a decline in mercury levels for several seabird species over 47 years. However, they traced that decline to a dietary switch from high-sulfate, mercury-rich fish to low-sulfate, mercury-poor fish. Thus, there was no overall change in mercury levels.

Continued

Feather-munching bacteria damage wild bird plumage

Date:July 13, 2016

Source:Central Ornithology Publication Office

A new study in The Auk: Ornithological Advanceslinks feather-degrading bacteria to damaged plumage on wild birds for the first time, offering new insights into how birds' ecology and behavior might affect their exposure to these little-studied microbes.

Scientists know surprisingly little about the diverse community of microbes that lives on bird feathers. A few of these species of bacteria can actually break down keratin, the material feathers are made of, but few studies have looked at how feather-degrading bacteria actually affect birds in the wild. Combining data from a decade's worth of bird-banding studies, Cody Kent and Edward H. Burtt of Ohio Wesleyan University found that tail-feather wear was strongly correlated with the presence of feather-degrading bacteria -- the first time this relationship has been demonstrated in live, wild birds.

Kent and Burtt's dataset included more than 3,500 birds from 154 different species captured between 1996 and 2005, in locations ranging from a rural Ohio backyard to Canada's Bay of Fundy to a Louisiana bayou. Researchers carefully wiped each bird's plumage across petri dishes containing a growth medium to culture any microorganisms living in the feathers. Ground-foraging, aerial-foraging, and fly-catching birds had a higher prevalence of feather-degrading bacteria, while nectivorous, tree-probing, and marine-foraging birds were less likely to harbor the microbes.

Read on ...