Recovery of benthic communities at Macquarie Island (sub-Antarctic) following a small oil spill

Intertidal communities at Macquarie Island (sub-Antarctic) were re-evaluated seven years after a small oil spill resulting from the grounding of the “Nella Dan”, and six years after the first assessment of biological impact. Sampling was conducted to evaluate community structure in three zones of the exposed rocky shore (upper red, kelp, and lower red) and in samples of Durvillaea antarctica holdfasts. There were no significant differences between the community structure in oiled and control locations in any of the three shore zones, but holdfast macrofaunal communities at oiled sites still showed evidence of impact. Holdfast community-structure in samples from heavily oiled sites showed moderate levels of recovery, with increased abundances of species which were considered sensitive to the oiling in the first post-impact studies and decreased abundances of opportunistic polychaete and oligochaete worms. In contrast, samples collected from the moderately oiled location at Secluded Bay showed little evidence of recovery. Holdfasts at this site were filled with sediment containing traces of diesel oil, and the macrofaunal community was dominated by opportunistic worms. This study clearly indicates that even small incidents of anthropogenic perturbation can have long-lasting consequences for marine communities at Macquarie Island. Received: 23 July 1997 / Accepted: 5 February 1998     

A Framework for Comprehensive,Integrated, Watershed Monitoring in New York City

The International Life SciencesInstitute (ILSI) Risk Science Institute (RSI) convenedan expert panel of scientists to developrecommendations for a comprehensive monitoring programfor the Croton and Catskill/Delaware watersheds, whichprovide drinking water to New York City's residents. This effort was conducted as part of efforts topreserve and enhance the quality of New York City'sreservoir system through a watershed protectionprogram. The panel developed recommendations for astrategic framework on which to construct a monitoringprogram. As part of this activity, the paneldetermined whether existing monitoring activities weredeficient and, where activities were deficient, thepanel developed recommendations for additionalinformation that should be collected.The panel recommended the development and use of anintegrated approach to watershed monitoring, whichdraws on modeling, risk-based planning and analysis,statistical sampling and design, and basic compliancemonitoring. The approach should be designed toprovide an assessment of natural and anthropogenicsources of stress to the system as well as anassessment of water quality trends in response tostresses acting in concert, both over the long termand over the five-year New York City Memorandum ofAgreement (MOA) assessment time frame. It should alsoprovide an assessment of the human health andenvironmental risks posed by a variety of stressors,and the impact of management actions implemented toameliorate stressors.     

Long-Term Relationship between Phosphorus Inputs and Wetland Phosphorus Concentrations in a Northern Everglades Marsh

Assessments of long-term relationships between changes innutrient inputs and wetland nutrient concentrations can becomplicated by fluctuations in other environmental factors aswell as by problems typical of long-term monitoring data.Consequently, statistical analysisof these types of data sets requirescareful consideration of environmental covariates, potentialbiases in the monitoring design, and irregularities caused bychanges in field sampling protocols. We evaluated therelationship between anthropogenic phosphorus (P) inputs andwater-column total P (TP) concentrations in a northernEverglades marsh by statistically analyzing available datacollected from several sampling programs over the past 20 years(1978–1997). Canal inputs of agricultural runoff contributemost of the P to the marsh and have produced a zone ofenrichment within the marsh during the past few decades.Regression analyses showed that both canal and marsh TPconcentrations increased during the 1980s and then decreased inthe 1990s. However, the statistical relationship between canal Pinputs and marsh TP, while significant, generally was weakexcept for marsh locations adjacent to the canal. Strongerrelationships existed between marsh TP and hydrologic parameterssuch as marsh water depth, which is controlled by changes inweather patterns and marsh management. In particular, dryconditions during the 1980s may have contributed to observedincreases in marsh P concentrations and the movement of a P`front' further into the marsh. Higher rainfall and water depthsand agricultural best management programs initiated during the1990s have been associated with reduced P concentrations incanal waters entering the marsh. While it is anticipated thatthis reduction eventually will result in lower marsh TPconcentrations, this effect is not yet evident, possibly due tointernal loading of P from enriched marsh soils. Our findingsillustrate some of the environmental factors that can complicateattempts to develop empirical relationships between P inputs andwetland P concentrations and to use such relationships to forecast changesin marsh concentrations based on past monitoring data alone.     

Evaluation of Caging Designs and a Fingernail Clam for Use in an In Situ Bioassay

Two cage designs and fingernail clams(Sphaerium fabale) were evaluated for theirsuitability for use in in situ bioassays toassess the ecological condition of a stream andpredict ecological recovery potential. One design(referred to as tray design) was a modified plastictray about one-fourth full of small gravels andcovered with 1 mm fiberglass mesh. The second design(referred to as tube-plates) consisted of shortplexiglass tubes about one-third full of small gravelsand attached horizontally to a plexiglass plate. Oneend of each tube faced into the current; both endswere covered with mesh. Cages containing clams weredeployed at reference and impacted (test) sites forperiods of 70 to 135 d. Growth and survival were theprimary endpoints evaluated, but the tube-platesallowed isolation of individual clams so that natalityalso could be evaluated as an endpoint. Results ofbenthic macroinvertebrate surveys, performed foranother study, were included to help validate bioassayresults. Both cage designs yielded good quantitative,site-specific results for clam survival and growth;results for natality, though, were less conclusive. Clam survival and growth results were in good generalagreement with the results for the benthicmacroinvertebrate community surveys. At a site wherethe macroinvertebrate community was the mostdepauperate, clam mortality was always rapid. At asite where the condition of the macroinvertebratecommunity was only slightly less impacted than themost impacted site, clam growth was almost alwayssignificantly lower than at reference sites. Survivalof clams was significantly reduced in <25 d at thissite in some trials, but in other trials there waslittle mortality. At a minimally impacted site, clamsurvival was similar to that found at reference sites,and differences in clam growth were not detectableuntil after 40 to 50 d of exposure. The tube-platedesign was easier to use, allowed more flexibility inselection of response parameters, and required lesshandling time of test animals, thus, this was thepreferred design. Our results demonstrated thateither in situ bioassay design can be used toaugment monitoring and assessment programs. Their useas a predictor of ecological recovery, however,requires further evaluation.     

Selection and application of a rainbow trout toxicity testing procedure for screening Sacramento River Watershed, California samples

A number of procedures have been developed to assess toxic effects on the early life stages of salmonid fish. In this study 13 rainbow trout embryo development relatively short-term (7 to 90 day) procedures were reviewed. Three 7-day methods from the published literature and three modifications developed at AQUA-Science (A-S) were evaluated in the laboratory. Based on that evaluation, A-S methods were selected for screening surface water samples (A-S 1) collected in the Sacramento River watershed (California) and for conducting toxicity identification evaluations (TIE) to identify cause(s) of toxicity. Test control performance, test sensitivity, and reference toxicant response variability in the A-S 1 were superior to those in commonly used freshwater toxicity testing methods. The incidence of Sacramento River watershed samples resulting in a notable decrease in embryo development was very low. Of 260 samples screened only 16 (6%) resulted in statistically significant inhibition of embryo development. Of the 16 toxic samples, nine caused minimal (less than 20% abnormal development) and four marginal (less than 30%) toxicity. Samples collected from the agriculture-dominated Colusa Basin Drain and rangeland/forest-dominated Battle Creek on June 16, 2005 caused significant toxicity. TIE procedures indicated that cationic chemicals were the primary cause of toxicity. Metals analysis did not reveal concentrations sufficient to inhibit embryo development, so the most probable cause of toxicity in the two samples was cationic chemicals (perhaps surfactants?) or metals that were not included in the analytical screening.     

Assessing coastal waters of American Samoa: territory-wide water quality data provide a critical “big-picture” view for this tropical archipelago

The coastal waters of American Samoa’s five high islands (Tutuila, Aunu’u, Ofu, Olosega, and Ta’u) were surveyed in 2004 using a probabilistic design. Water quality data were collected from the near-shore coastal habitat, defined as all near-shore coastal waters including embayments, extending out to 1/4 mile off-shore. Hydrography and water column samples were collected, and water quality data were compared to the Territorial water quality standards for pH, dissolved oxygen (DO), Enterococcus, chlorophyll a, water clarity, total nitrogen, and total phosphorus. All station measurements for pH, DO, and Enterococcus satisfied the local water quality standards, although some fraction of the Territory could not be assessed for either DO or Enterococcus. With respect to chlorophyll a, 66 ± 18% of Territory coastal waters complied with the standard, while 34 ± 18% failed to comply with the standard. For water clarity, 54 ± 18% of the Territorial waters complied with the standard while 42 ± 7% failed to comply. Territorial waters satisfied the standards for total nitrogen and phosphorus 72 ± 17% and 92 ± 10%, respectively. These data provide the first “big-picture” view of water quality in the near shore region around the high islands of American Samoa. While the picture is encouraging, these data suggest emerging water quality concerns.     

Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, <Emphasis Type="Italic">Megalopta genalis</Emphasis> (Halictidae)

Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis.     

Calculation of the Charging Rate of Fine Particles by Unipolar Ions

Theories of particle charging based on boundary value solutions to the diffysional equation may not be applicable to electrostatic precipitators where the ion density is rarely more than an order of magnitude greafer than the particle concentration. A new charging equation, based on kinetic theory, is presented which evaluates the charging rate in terms of the probability of collisions between the flust particles and ions. In the presence of an external electric field, the surface of the particle is divided into three charging regions, and separate charging rates are calculated for each region. The total charging rate is the sum of these three individual rates. For large particles and high electric fields, this theory predicts essentially the same charging rate as the classical field charging equation of Rohmann and Pauthenier. For low electric fields, the theory reduces to White’s diffusional charging equation. Agreement is within 25% of Hewitt’s experimental results over the entire range of variables where data are available. For practical charging times, agreement is within 15%.