UROP Project

Effects of human activities on aquatic ecosystems

Measure 1: Sharpening the Scientific Profile

Effects of Agriculture: It is well known that agriculture can degrade of stream and river ecosystems due to the runoff of sediments, pesticides and nutrients into surface waters. Fertilizers from agriculture are one of the largest sources of nutrients to Canadian waters and elevated concentrations are associated with problems such as nuisance algal growth and reductions in the ability of aquatic systems to support life. Sediment pollution affects streams by smothering organisms and fish spawning beds, and by reducing the ability of plant life to grow because of decreases in water clarity. Nutrients and sediments are common, co-existing stressors in streams within agricultural watersheds, but our understanding of their effects on aquatic organisms is based mainly on studies of individual stressors and at lower levels of biological organization (i.e. populations or specific assemblages within a food web). The effects of the combination of stressors on stream ecosystems and how responses vary across gradients of human activity/agricultural intensity are not well understood. A promising approach for assessing effects of several agricultural stressors on stream biota is through the analysis of animal and plant tissues for stable carbon and nitrogen isotope ratios (Grey 2006, Peterson and Fry 1987). Predictable variation in these measurements between trophic levels and different food sources or habitats allows for the trophic position of food web organisms (nitrogen) and their sources of energy (carbon) to be identified and compared across streams with different levels of human activity (Anderson and Cabana 2007, Finlay et al. 2002).

Task

To understand how agricultural activity affects aquatic food webs, we will collect and analyze algae, invertebrates and fish from 20 streams within the potato production region of New Brunswick. These streams will be selected across a range of land use activity and other sampling will include stream gauge measures to assess flow, rapid assessment techniques to determine vegetation cover, and water chemistry for nutrients. This sampling will occur over several trips in July through September and will use standard techniques. Fish, invertebrate and algal samples will be coarsely sorted on site and brought back to the lab for further identification and processing. Whole, pooled invertebrates and algae, and fish muscle tissues will be processed for stable isotope analyses. These results will be used to understand whether sediment and nutrient inputs from agriculture changes how energy flows through aquatic systems and the dietary habits of resident organisms. Mercury Kejimkujik National Park (KNP), located in southwestern Nova Scotia, Canada, has been designated a mercury (Hg) “hotspot” due to high concentrations of Hg found in common loons (Gavia immer) and their main prey, yellow perch (Perca flavescens) within the park. Concentrations of total Hg in yellow perch in KNP have increased over the last decade, and many currently exceed the levels suspected to affect the health of the fish themselves. However, little is known about the effects of Hg on wild fish. To determine whether the elevated Hg is negatively affecting the general and reproductive health of this species, sexually mature male and female yellow perch were collected in the fall of 2009 and 2010 from 12 lakes known to contain perch with differing Hg concentrations. Fish were weighed and measured and tissues (blood, liver, gonad, muscle) were collected to assess their Hg concentrations and its effects. Several health variables such as condition, liver and gonad size, and egg development are being examined in these fish and compared between lakes. Within liver tissues, there is a higher incidence of tissue damage in fish containing higher concentrations of mercury. The effects of Hg seen in these wild perch may be also occurring in other wild fish populations; a concern given that Hg is a global pollutant. The student should join for the field work and conduct ecological and ecotoxicological work, eg micronucleous assay with erythrocytes from fish.

Requirements

The applicant should have sound experimental experience in ecotoxicology/ecology and interests in field word.

Full Address

Biology Department, Saint John, New Brunswick, Can
P.O. Box 5050, Tucker Park Road,
E2L 4L5 Saint John, New Brunswick,
Canada
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