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Harvard Forest Data Archive

HF094

Physiological Ecology of Euryhaline Chironomid Midges in Cape Cod MA 2002-2003

Related Publications

Data

Overview

  • Lead: Elizabeth Colburn, John Portnoy
  • Investigators:
  • Contact: Elizabeth Colburn
  • Start date: 2002
  • End date: 2003
  • Status: completed
  • Location: Pilgrim Lake / East Harbor (Truro MA)
  • Latitude: +42.06
  • Longitude: -70.13
  • Elevation: 0 to 1 meter
  • Taxa: Chironomus decorus
  • Release date: 2006
  • Revisions:
  • EML file: knb-lter-hfr.94.16
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: regional studies; watershed ecology
  • LTER core area: populations
  • Keywords: insects, restoration, salinity, salt marshes, wetlands
  • Abstract:

    In summer, 2002, hundreds of thousands of salt-tolerant midges (Chironomus decorus group, Diptera, Chironomidae) emerged from Pilgrim Lake/East Harbor, Truro, MA. The lake is a former estuary but has been separated from the sea for over 150 years by restrictions associated with railroad and highway construction. Brackish conditions caused by leaky tide gates designed to drain excess freshwater from the lake, coupled with high nutrient levels exacerbated by a massive fish kill the previous year, created conditions that supported densities of midge larvae of more than 5,000/m2 and produced a severe public nuisance in the vicinity of the lake when the adult midges emerged. The emergence coincided with National Park Service efforts to increase tidal flow into the lake, as part of a long-term commitment to restoration of restricted coastal waters within the Cape Cod National Seashore. We are studying the effects of increased tidal flow on midge populations, and in particular evaluating how high salinities need to be to reduce the potential for further nuisance outbreaks of the midges.

  • Methods:

    In response to initial nuisance levels of midges, National Park Service personnel began monitoring larval densities and lake salinities in the field in 2002. Initial spot sampling has been expanded to include both sampling across an east-west transect in the lake and random sampling across the basin for estimation of overall population levels. Larvae are sampled with a corer (diameter), sieved (500 um mesh), and counted. Salinities are measured using a hand-held refractometer with periodic calibration using a conductivity bridge. For experimental assessment of effects of salinity and temperature on midge populations, we sieved larvae from lake sediment in late 2002 and early 2003, and maintained them in the laboratory in shallow (10 cm deep) trays filled with natural substrate and lake water or artificial seawater. In controlled experiments, larvae were held at salinities of 0-35 % at low temperatures (0-4 C) comparable to winter ambient conditions, and their survival was monitored over time. Subsequent experiments investigated effects of salinity and temperature on pupation and adult emergence.

  • Use:

    This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.

  • Citation:

    Colburn E, Portnoy J. 2006. Physiological Ecology of Euryhaline Chironomid Midges in Cape Cod MA 2002-2003. Harvard Forest Data Archive: HF094.

Detailed Metadata

hf094-01: midge data

  1. exp.sal: experimental salinity of artificial seawater prepared for experiments (parts per thousand, g/liter) (unit: gramsPerLiter / missing value: NA)
  2. ac.pre.ref: salinity of artificial seawater solutions as determined by refractometer reading at start of acute experiment (5 larvae held at each salinity for 72 hours at 4 degrees C) (parts per thousand, g/liter) (unit: gramsPerLiter / missing value: NA)
  3. ac.post.ref: salinity of artificial seawater solutions as determined by refractometer reading end of acute experiment (5 larvae held at each salinity for 72 hours at 4 degrees C) (parts per thousand, g/liter). (a), (b), (c) = experimental jar a, b, or c (unit: gramsPerLiter / missing value: NA)
  4. ac.surv: percent of 5 larvae surviving at experimental salinities after 72 hours at 4 degrees C (percent) (unit: dimensionless / missing value: NA)
  5. lt.pre.ref: salinity of artificial seawater solutions as determined by refractometer reading at beginning of long-term survival experiment (3 replicates per salinity, 8 larvae/replicate except for 7 ppt (c), which had 9 larvae, held at 7 degrees C) (parts per thousand, g/liter). (Ac) = acute, 72-hour experiment; (LT) = long-term survival at 7 C; (Em) = emergence at ambient temperature. (unit: gramsPerLiter / missing value: NA)
  6. lt.cond: specific conductance of artificial seawater solutions at the beginning of the long-term survival experiment (uS/cm at 25 C) (unit: microsiemensPerCentimeter / missing value: NA)
  7. lt.surv.a: percent of larvae surviving at experimental salinities after 25 days at 7 degrees C (3 replicates per salinity, 8 larvae/replicate except for 7 ppt (c), which had 9 larvae) (percent survival). (a), (b), (c) = experimental jar a, b, or c for each experimental salinity (unit: dimensionless / missing value: NA)
  8. lt.surv.b: percent of larvae surviving at experimental salinities after 25 days at 7 degrees C (3 replicates per salinity, 8 larvae/replicate except for 7 ppt (c), which had 9 larvae) (percent survival). (a), (b), (c) = experimental jar a, b, or c for each experimental salinity (unit: dimensionless / missing value: NA)
  9. lt.surv.c: percent of larvae surviving at experimental salinities after 25 days at 7 degrees C (3 replicates per salinity, 8 larvae/replicate except for 7 ppt (c), which had 9 larvae) (percent survival). (a), (b), (c) = experimental jar a, b, or c for each experimental salinity (unit: dimensionless / missing value: NA)
  10. lt.post.ref.a: salinity of artificial seawater solutions in long-term survival experiment, as determined by refractometer reading, in each of three jars(x) for each salinity treatment, after 25 days at 7 degrees C (parts per thousand, g/liter). (a), (b), (c) = experimental jar a, b, or c (unit: gramsPerLiter / missing value: NA)
  11. lt.post.ref.b: salinity of artificial seawater solutions in long-term survival experiment, as determined by refractometer reading, in each of three jars(x) for each salinity treatment, after 25 days at 7 degrees C (parts per thousand, g/liter). (a), (b), (c) = experimental jar a, b, or c (unit: gramsPerLiter / missing value: NA)
  12. lt.post.ref.c: salinity of artificial seawater solutions in long-term survival experiment, as determined by refractometer reading, in each of three jars(x) for each salinity treatment, after 25 days at 7 degrees C (parts per thousand, g/liter). (a), (b), (c) = experimental jar a, b, or c (unit: gramsPerLiter / missing value: NA)
  13. emerge.a: Percentage of animals held at each salinity in jars a, b, or c that emerged successfully as adults. Larvae were initially held at experimental salinities for 25 days at 7 C, then transferred to ambient temperature and held until all had emerged or died; 3 replicates per salinity, 8 larvae per replicate (except for 7 ppt(c), which had 9 larvae) (percent emergence). (a), (b), (c) = experimental jar a, b, or c. (unit: dimensionless / missing value: NA)
  14. emerge.b: Percentage of animals held at each salinity in jars a, b, or c that emerged successfully as adults. Larvae were initially held at experimental salinities for 25 days at 7 C, then transferred to ambient temperature and held until all had emerged or died; 3 replicates per salinity, 8 larvae per replicate (except for 7 ppt(c), which had 9 larvae) (percent emergence). (a), (b), (c) = experimental jar a, b, or c. (unit: dimensionless / missing value: NA)
  15. emerge.c: Percentage of animals held at each salinity in jars a, b, or c that emerged successfully as adults. Larvae were initially held at experimental salinities for 25 days at 7 C, then transferred to ambient temperature and held until all had emerged or died; 3 replicates per salinity, 8 larvae per replicate (except for 7 ppt(c), which had 9 larvae) (percent emergence). (a), (b), (c) = experimental jar a, b, or c. (unit: dimensionless / missing value: NA)