Learning aquatic biology to save plankton!

Updated: Jun 30, 2019

In order to learn about aquatic biology knowledge and enter the world of water, I along with 3 other students in my team participated in the practice activities of the Simeitang aquatic life survey in Wuhan.

The contents of this survey are phytoplankton, zooplankton, and benthic animals and the activities include the collection and identification of aquatic organisms. Among them, aquatic organisms refer to aquatic plants, aquatic animals and plankton.

1) Investigate methods and procedures

Water samples were collected using a water collector and filtered using a plankton net to collect plankton samples; the mud was collected using a mud collector to collect benthic animals and the samples were identified.

Phytoplankton

The collection of phytoplankton includes qualitative collection and quantitative collection.

Qualitative collection: The plankton nets made using a No. 25 sieve were towed in water and collected in a 50 mL graduated vial. Add Lugol's solution to fix (fixed dose is 1% of water sample, when water bloom or algae is more than appropriate, the fixative may be added as appropriate). It is necessary to store the sample for a long time, and then add about 5 mL of formalin solution to the water sample.

Quantitative collection generally uses a water collector to take a 0.5 m water sample (according to the depth of the water body or the requirements to determine the sampling level), and put it into a 1L PE plastic bottle. The fixed step is the same as the qualitative acquisition. The sample bottle containing the water sample was placed in the dark for 48 h, and then concentrated by a siphon method to a final concentration of 30 mL or 50 mL. Save for inspection.

Zooplankton

(1) Protozoa and rotifers: Generally, phytoplankton in the same section shares a qualitative and quantitative sample with protozoa and rotifers.

(2) cladocerans and copepods: Qualitative collection The plankton net made of No. 13 sieve was dragged and collected in water. The sample in the net head was placed in a 50 mL graduated sample vial and fixed in 4-5% formalin solution.

For quantitative collection, the water sample of 10 L-50 L (the sampling volume is determined according to the number of zooplankton) is filtered by a plankton net made of 25 mesh sieve, and the sample in the net head is placed in a 50 mL sample. In the bottle, finally wash the net head in the water for 2-3 times (note: do not immerse the liquid in the plankton net), continue to collect the rinsing liquid into the sample bottle, and fix it with 4-5% formalin solution. Save for inspection.

Benthic

The collection of benthos varies according to the type of water, and the sampling methods are different. Reservoir, lake (the water is deep, or the sediment is sediment, etc.)

The benthic animals were collected using a 1/16 m2 Peterson mud concentrator. The sediment was collected and washed through a 60-mesh sieve. The residue was placed in a ziplock bag, and the appropriate amount of water was added back to the laboratory. Benthos was detected and placed in 50 ml plastic specimen bottles and stored in 10% formalin. Stream waters (lighter water, can be collected directly into the water)

The benthic animals were collected using a 40 mesh diameter and a sampling area of 0.09 m2 in the direction of the water flow to the river bed. The benthic animals on the surface of the stone were brushed into the net and the substrate was agitated. Randomly collect 5 replicates, coarsely filter through 40 mesh gauze, dispense into 5 specimen bottles, and store with 95% ethanol. Add excess residue to five ziplock bags and add the appropriate amount of water, specimen bottle, and a ziplock bag. After being brought back to the laboratory, they are sorted and counted.

The qualitative samples of benthic animals were classified and identified by anatomical mirror and microscope. The quantitative samples were counted according to different types of individuals. The population number was calculated according to the area of the mud collector. The sample was filtered to remove excess water and then weighed with wet weight. Calculate the number and biomass of benthic animals.