a limnological assessment: the lucas pond

A Limnological Assessment: The Lucas PondChristian BrownDylan GollenTaylor LasleyJohn Novak

Overview

• Objectives• Methods and Materials• Results• Discussion• Implications

Team Objectives

Sediment Analysis

Macro Invertebrate Assessment

• Identify species present• Enumerate densities

• Water content• Organic matter

Methods and Materials

Field Equipment

• KB Core sampler• Ekman grab sampler• Pencils, notebook, tape • Storage containers

Lab Equipment

• Digital scale and weigh boats• Oven• Metric ruler

Methods and MaterialsSampling Design• KB core and Ekman samples were taken in a balanced manner

that encompassed the greatest area of the pond • Seven samples total for each sampling method• Two samples from east and west sites• Three replicates from middle site

Methods and Materials

Methods and Materials

Analyzing KB Core SamplesWater Content• measured total core depth (cm)• removed 1cm sections • recorded wet weights of each

section• placed samples in oven, then

recorded dry weights

Percent Water Content = Wet weight-dry weight/wet weight

Methods and Materials

Methods and Materials

Organic Matter• Placed dried samples into

oven for burning

• Recorded ash weight

Percent organic matter = dry weight – burn weight/ dry weight

Methods and MaterialsBenthic macro invertebrates• collected with Ekman grab

sampler• Same sample sites• Samples filtered through wash

bucket (remove sediment)• samples were stored and

preserved in ethanol solution • species identified and

enumerated using dissecting microscopes

• densities were converted from Ekman volume (225cm2) to number per square meter

Results

Figure 2.-Plot of water content versus sediment depth for the Lucas pond in Latah Co. Moscow, Idaho USA on October 9, 2013.

Results

Figure 1. - Plot of organic matter versus sediment depth, using core sections taken with a KB corer at the Lucas pond in Latah Co. Moscow, Idaho USA on October 9, 2013.

Results

Table 1. Paired t-test for organic matter and water content between the east and west sample sites in the Lucas pond on October 9, 2013.Sample t df n p Organic Matter (%) 3.412224599 9 10 0.007722 Water Content (%) 13.55686461 9 10 2.71E-07

Results

Sample t df n pBenthic Macro -2.178199633 2 3 0.080636

Table 2. Paired t test between benthic macro invertebrate counts from the east and west sampling sites in the Lucas

pond on October 9, 2013.

Discussion

Sediment Accumulation

• Pond size• Steep catchment• Surrounded by granitic

Gneiss rock• Allocthonous inputs

from vegetation and rock

Discussion

Benthic Macro-Invertebrates• Relatively high abundance • Chaoborus, Chironimids, and

Oligochetes contribute to bioturbation (Ademek et al. 2009)

• Mechanical mixing of sediment through construction of feeding tubes and burrows

• Affects transport of nutrients, particularly P and N

• Increases oxygen penetration into sediment which enhances mineralization process by which nutrients are released into the overlying water

• Inhibition of phytoplankton and benthic macrophyte growth

• Chironomid larvae can increase nutrient enrichment which can eventually lead to eutrophication

Implications• When considering the benthic aspects of the Lucas pond the

longevity is dependent upon:

• High rates of total sediment and organic matter accumulation• Unchecked population of benthic macro invertebrates could

diminish pond water quality through process of bioturbation

Literature cited• Ademek, Z. Marsalek, B. 2013. Bioturbation of sediments by

macroinvertebrates and fish and its implication for pond ecosystems: a review. Aquaculture Int. 21:1-17

• Brainard, A. S. Fairchild, G.W. 2012. Sediment characteristics and accumulation rates in constructed ponds. Journal of Soil and Water conservation. Vol. 67, no. 5. pp. 425-432

QUESTIONS