Winona State University
BIOL 415/527 – ECOLOGY OF LARGE RIVERS

LAB EXERCISE #2

SUBMERSED MACROPHYTE SURVEYS

OBJECTIVE

Submersed macrophytes often dominate the backwater habitats of the upper Mississippi River. This exercise will familiarize you with many of the various species of submersed macrophytes in the region, and introduce you to a standardized method for assessing these types of aquatic plants.

HYPOTHESIS

Submersed macrophytes will display high abundance, but low diversity, in the Crooked Slough area of the upper Mississippi River.

METHODOLOGY

The abundance and diversity of submersed aquatic plants will be examined in various habitats in and around Crooked Slough. The following describes the general procedure we will follow to examine the hypothesis listed above.

Field procedures:

Macrophytes will be collected from shallow water habitats by using a long-handled metal rake.

1) Lower the rake head vertically into the water all the way to the substrate.

2) While keeping the rake head near the bottom, draw the rake back toward the boat, rotate the rake three full turns to entangle the plants.

3) Lift the rake head back to the surface in a manner to best retain plants, and lift the rake and plants collected into the boat.

4) Rate and record the density of plants collected on a scale of 0 to 5, using the following guidelines:

0 – no plants collected

1 – 1 to 20% of rake tine filled with plants (based on tine length from base to tip)

2 – 21 to 40% of rake tine filled with plants

3 – 41 to 60% of rake tine filled with plants

4 – 61 to 80% of rake tine filled with plants

5 – 81 to 100% of rake tine filled with plants

5) Wash all plants collected in the water-filled plastic tote, spread out on the sorting table, and separate plants into groups based on species (use the field guide for identification when needed).

6) Place plants, one species at a time, into salad spinner to remove excess water, weigh on the portable balance, and record species and weights on the data sheet.

ANALYSIS

1) For each sample, use the species’ weights to calculate a Simpson diversity value. Calculate the average (and SD) of these diversities. Are diversities high, low, or moderate?

2) Calculate an average plant density (and SD) using the rake tine scores for all samples. Rate your average density compared to a maximum value of 5.

3) Combine each species’ weights from all samples to develop a list of all species collected and their weights. Create a graph with plant weights on the Y axis, and plant species on the X axis (assign each species a number, with the most abundant species as 1, next most abundant as 2, and so on). Do the values form a pattern?

EQUIPMENT

Long-handled rakes

Large-capacity salad spinner

Portable balance

Return to ELR lab

Neal D. Mundahl
Winona State University
Winona, MN 55987-5838