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Research topics

Environmental Chemistry

water processing

Why measure water chemistry?
Physical and chemical measurements of lakes and streams are critical to describing the condition and source of the water, the suitability of the water for human and livestock use, and for understanding the distribution of aquatic biota.

How do we sample water chemistry?
Water chemistry is typically measured in the field using electronic probes, which give immediate data, or back at the lab on either whole water samples (total chemical measures) or filtered water samples (dissolved chemical constituents), which requires water to be collected in the field. Water samples are processed in camp in preparation for shipping and lab analysis.

What do we measure?
Typical field measurements include descriptions of the lake (depth, size, habitats) and some physico-chemical measurements (pH, conductivity, dissolved oxygen, Secchi depth). In the lab we measure major ions, nutrients, carbon (organic and inorganic), and stable isotopes.

What have we learned about Mongolian water quality?
Many lakes and streams in western Mongolia are suffering from poor water quality. Additionally, many water bodies and springs have dried up, likely as a result of global warming.

For available environmental chemistry data, visit the Mongolia Environmental Database page.



What are diatoms?
Diatoms are a large group of microscopic "algae" that grow as single cells or small colonies and are characterized by an ornamented, two-part cell wall made of biogenic opaline silica (biological glass). Diatoms are an important part of the primary producer community in most aquatic habitats, even ephemerally moist habitats such as soil. They often live within narrow environmental conditions, thus diatom communities can be indicative of pollution, water temperature, water depth, nutrient levels, or salinity.

How are they collected?
Diatoms are collected using plankton nets, substrate scrapes, sediment dredges and sediment coring. Collections are either dried or preserved with alcohol or formalin.

How are they used in research?
In addition to discovering new species in Mongolia, diatoms are most widely studied in lake sediment cores and used as evidence of changing conditions in lakes. In Mongolia changes in lakes are a result of climate and landuse change.

What have we learned about Mongolian diatoms?
The distribution of diatom species in western Mongolia is largely controlled by nutrients and salinity. As a result we have developed models that allow us to infer historical water quality from fossil diatom communities.



What are ostracodes?
Mussel shrimps, or Ostracoda, are small Crustacea, with two shells. Brine shrimp, barnacles, shrimp, crabs and lobsters are all crustaceans. Their calcified carapaces (two articulating shells made of calcite, a calcium carbonate mineral) have length of about 0.4 up to 8 mm and completely envelop the soft body. Ostracodes occur in a variety of marine and freshwater environments. They are usually found in benthic and periphytic communities, but also occur in (semi-) terrestial habitats and groundwater. In spite of their general presence in aquatic habitats, this group is little-studied relative to other microscopic bottom-dwelling crustaceans.

How are they collected?
Ostracodes are sampled from near-surface sediments or aquatic vegetation using nets, grabs, or dredges and are isolated using graded sieves. Shallow water habitats or springs are sampled with smaller nets, pipettes, or a simple peristaltic pump. Ostracode samples are immediately preserved (EtOH) or sorted using field microscopes.

How are they used in research?
First, they must be identified. Correct specific and even generic identification of ostracodes generally requires full dissection. The skill to do this properly can take months to learn. New species are still being discovered. Because their shells are made of calcite, ostracode shells are often preserved in sediment cores. Both species assemblages and shell chemistry can provide clues about past environment, and climate.

What have we learned about Mongolian ostracodes?
Ostracode distribution in lakes of Western Mongolia is affected by salinity and ionic composition, altitude, and nutrient status (nitrogen, phosphorus,…). Species diversity in springs is generally higher than in lakes.

For available ostracode data, visit the Mongolia Ostracode Database page.



What are chironomids?
Chironomids (Family Chironomidae) are a family of flies that are primarily aquatic during their larval and pupal stages. Although some taxa are semi-aquatic, the great biological diversity of the family is linked to species radiation within standing and running freshwaters. In small streams of the mid-latitude Holarctic Region, where diversity has been most thoroughly investigated, the Chironomidae generally are the most species-rich group of aquatic insects, often comprising 50% or greater percentages of the fauna.

How are they collected?
Chironomids can be found in lakes, streams, springs, and associated wetland and marginal semiaquatic habitats. Collection methods consist of emergence trapping, light trapping and sweep netting for adults, collections of surface-floating pupal exuviae (SFPE), and hand picking benthic substrates and aquatic vegetation for larvae and/or pupae.

How are they used in research?
Many chironomid species or parts of their life history remain to be discovered. Chironomids are also widely used as bioindicators for water quality assessment. Their head capsules (shed as the larvae molt) are preserved in lake sediments and used as indicators of past temperature or hypolimnetic oxygen levels.

For available chironomid data, visit the Mongolia Chironomid Database page.



What is paleolimnology?
Paleolimnology is the study of lake sediments to understand the environmental history of lakes and landscapes.

How do we take sediment cores?
Sediment cores are collected with coring devices that are operated from anchored boats (or from the ice surface in winter). Two main types of corers are gravity corers, which essentially push an open tube into the sediment, and piston corers, which use a piston to assist penetration of the core tube into the sediments. Gravity corers can take cores up to 30 cm in length, whereas the piston corer we used in Mongolia could take a core up to 1.8 m long.

What lake mud can tell us?
We first date the cores using radioisotopes such as 210-Pb, which produces a date model for about the last 200 years. Them we look at both biological and chemical signals (called proxies) in the core. For example, charcoal in a core give the fire history of the landscape around a lake, inorganic matter in a core may be a record of erosion or wind transported minerals, and diatoms are a record of how the algal community has changed over time. Together, the proxies give us a historical picture of how a lake and its landscape have changed over time.

What have we learned from Mongolian lake sediments?
Charcoal records in lake sediments suggest that incidence of fire is very low in Mongolia and has gotten even more infrequent as grazing intensifies. Recent lake sediment records (<100 yr) verify that many lakes in western Mongolia are becoming increasing eutrophic.

For available paleolimnology data, visit the Mongolia Sediment Core Database page.