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USGS1967

Magruder Park Swamp

The last Tuesday in August, between five-thirty and seven in the evening, we zigzaged through this glorious jungle, attended by a family of Wood Pewees for whom we seemed to be stirring up a feast of flying insects. There was gentle background music by Mole Crickets. A few steps in from the playing field and we were out of sight in ten-foot-high Cattails. All through, we met -- as high as we, or higher--clumped Cinnamon Ferns, deep-rose Joe Pye Weed, and orange, pendent flowers of Jewelweed (first cousins to Balsam and Sultana). Here and there were soft, white spikes of Canadian Burnet, a rare plant hereabouts, and deep purple Ironweed. Dense-foliaged Hempweed climbed over bushes and up small trees, filling the air with its delicate fragrance. Arrowleaf Tear-thumb snatched at us with tiny prongs on its angled stems. Once in a while we tripped over huge sedge tussocks, half-hidden in the tangle. A few times we steered around a small bush of Poison Sumac. The next day We remembered seeing ninety kinds of plants on this hasty trip. Skunk Cabbage leaves recalled April, when a person, from the edge of the lawn, could see huge clumps of them all the way across the swamp. The sky had been washed by last week's downpours; scattered Gums were reddening; and Maples were getting ready for crimson beauty a month from now. There wasn't a mosquito! (Ed. Note.-The Hyattsville City Council is taking pains to preserve this interesting swamp.)

Prince Georges Post↗

USGS2014

Temporal patterns in the foraging behavior of sea otters in Alaska

Activity time budgets in apex predators have been proposed as indicators of population status relative to resource limitation or carrying capacity. We used archival time-depth recorders implanted in 15 adult female and 4 male sea otters (Enhydra lutris) from the northernmost population of the species, Prince William Sound, Alaska, USA, to examine temporal patterns in their foraging behavior. Sea otters that we sampled spent less time foraging during summer (females 8.8 hr/day, males 7.9 hr/day) than other seasons (females 10.1–10.5 hr/day, males 9.2–9.5 hr/day). Both sexes showed strong preferences for diurnal foraging and adjusted their foraging effort in response to the amount of available daylight. One exception to this diurnal foraging mode occurred after females gave birth. For approximately 3 weeks post-partum, females switched to nocturnal foraging, possibly in an effort to reduce the risk of predation by eagles on newborn pups. We used multilevel mixed regression models to assess the contribution of several biological and environmental covariates to variation in the daily foraging effort of parous females. In the random effects only model, 87% of the total variation in foraging effort was within-otter variation. The relatively small among-otter variance component (13%) indicates substantial consistency in the foraging effort of sea otters in this northern population. In the top 3 models, 17% of the within-otter variation was explained by reproductive stage, day length, wind speed, air temperature and a wind speed × air temperature interaction. This study demonstrates the potential importance of environmental and reproductive effects when using activity budgets to assess population status relative to carrying capacity.

Alaska↗

USGS2011

Trends in sea otter population abundance in western Prince William Sound, Alaska: Progress toward recovery following the 1989 Exxon Valdez oil spill

Sea otters in western Prince William Sound (WPWS) and elsewhere in the Gulf of Alaska suffered widespread mortality as a result of oiling following the 1989 T/V Exxon Valdez oil spill. Following the spill, extensive efforts have been directed toward identifying and understanding long-term consequences of the spill and the process of recovery. We conducted annual aerial surveys of sea otter abundance from 1993 to 2009 (except for 2001 and 2006) in WPWS. We observed an increasing trend in population abundance at the scale of WPWS through 2000 at an average annual rate of 4 percent: however, at northern Knight Island where oiling was heaviest and sea otter mortality highest, no increase in abundance was evident by 2000. We continued to see significant increase in abundance at the scale of WPWS between 2001 and 2009, with an average annual rate of increase from 1993 to 2009 of 2.6 percent. We estimated the 2009 population size of WPWS to be 3,958 animals (standard error=653), nearly 2,000 animals more than the first post-spill estimate in 1993. Surveys since 2003 also have identified a significant increasing trend at the heavily oiled site in northern Knight Island, averaging about 25 percent annually and resulting in a 2009 estimated population size of 116 animals (standard error=19). Although the 2009 estimate for northern Knight Island remains about 30 percent less than the pre-spill estimate of 165 animals, we interpret this trend as strong evidence of a trajectory toward recovery of spill-affected sea otter populations in WPWS.

Alaska↗

USGS2019

A ship's ballasting history as an indicator of foraminiferal invasion potential--An example from Prince William Sound, Alaska, USA

We investigated the potential role of ballast sediment from coastal and transoceanic oil tankers arriving and de-ballasting in Port Valdez as a vector for the introduction of invasive benthic foraminifera in Prince William Sound, Alaska. Forty-one ballast sediment samples were obtained in 1998-1999 from 11 oil tankers that routinely discharged their ballast in Prince William Sound after sailing from other West Coast (Los Angeles/Long Beach Harbor, San Francisco Bay, and Puget Sound) or foreign ports (Japan, Korea, and China) where they originally ballasted. Forty of these samples contained benthic foraminifera, including 27 (66%) with the introduced species Trochammina hadai Uchio from nine (81%) of the ships. In all, 59 species were recovered and foraminiferal abundance peaked at 27,000 specimens per gram dry sediment. Of the 41 samples, three were stained and living benthic foraminifera were recovered in all three of them. The entrained foraminifera reflected the number of times ballasting occurred (single or multiple sources), the location of ballasting (estuarine or offshore), and post-acquisition alteration of the sediment (i.e., growth of gypsum crystals at the possible expense of calcareous tests). In temperate regions, sediment samples resulting from single-source ballasting in estuaries (SSBE), multiple-source ballasting in estuaries (MSBE), single-source ballasting offshore (SSBO), and a combination of SSBO and SSBE or MSBE, typically contained increasingly higher species richness, respectively. The potential for an invasion is dependent on the presence of viable candidates and their survivability, their abundance in the ballasting location, and the number of times ballasting occurs, most of which are evident from the ship’s ballasting history. Trochammina hadai is a good example of a successful invasive in Prince William Sound for the following reasons: 1) the species is abundant enough in West Coast and foreign ports where ballasting occurs that sufficient individuals needed for reproduction may be transported to the receiving waters; 2) Port Valdez, in particular, receives repeated and frequent inoculations from the same source ports where T. hadai is present; 3) large quantities of sediment are taken up by commercial vessels during ballasting and benthic foraminifera occur in abundance in ballast sediment; 4) ballast sediment provides a suitable environment in which benthic foraminifera can survive for extended periods of time during transport; 5) T. hadai flourishes in a wide range of temperatures and environmental conditions that characterize both the ports where ballasting takes place as well as in Port Valdez where de-ballasting occurs; and 6) the species is capable of asexual reproduction and possibly the ability to form a dormant resting stage, both of which have the potential to lower the threshold for colonization. Clearly, ballast sediment is a viable vector for the introduction of T. hadai and other invasives into Alaskan ports and elsewhere worldwide.

Alaska↗