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Methods Manual for Managers: 

      Field Techniques for Algal Research


These methods were developed for research with the Hawaii Coral Reef Initiative Program and are being compiled for a Methods Manual to be distributed by HCRI.  The manual was written by Linda Preskitt and edited by Celia M. Smith and I.A. Abbott of the University of Hawaii, Botany Department, Honolulu, Hawaii.


Algal Collection


     Handling and Pressing

Photoquadrat Survey

     Photoquadrat Framer

Light Measurement

Alizarin Stain

Nutrient Enrichment

Sediment Traps


To estimate the quantity of sediment deposited on a daily basis (mg/cm2/day).


Materials for one sediment trap

One plastic garden tray

Two 2" x 7.5" (standard) bricks

Six 6" pieces of 2" PVC pipe

Twelve 2" PVC endcaps

PVC glue

Cable ties

#6 Melitta coffee filters

Six large plastic automotive funnels

to hold filters

Funnel rack (any plastic rack)
Scale (0.01 gm precision)


Hobo light meter in underwater housing

(See Light Intensity Measurement method)




1. Cut 3 holes in the garden tray through which the 2" PVC pipe will fit snugly.

2. Attach two bricks underneath the inverted garden tray with cable ties, one on each uncut corner.

3. Attach optional equipment to base with cable ties.


1. Cut six 6" lengths of the 2" PVC pipe.

2. Glue one PVC endcap on each piece of pipe.

3. Label the bottom of each PVC pipe with permanent marker. (Coralline algae may deposit on top and sides of pipe obscuring any markings in those areas.)


Place assembled sediment traps flat on hard or sandy substrate. Avoid coral when possible. In areas of potential surge or high wave action, cable tie sediment trap base to substrate. Also avoid the bottom of sandy grooves that may experience bottom sediment churning in times of greater water motion, causing high readings of sediment loading. Depending on the turbidity and wave action in the area, sediment traps should be collected weekly, bi-monthly or monthly.


Collecting Sediment Traps

Remove each PVC pipe carefully by reaching under the base and pulling the trap down through the hole. Cap the open end with the extra PVC endcap. If continuing the sediment collection, insert new PVC pipes. (Note: do not transport new PVC pipes capped as pressure makes it difficult to remove caps).



Lab Analysis

Sediments are rinsed, drained, and dried in #6 Melitta coffee filters held in plastic gas funnels placed upright in drying racks.


1. Label one filter for each collected sample. Weigh filter 3 times. Average and record weight in notebook.


2. Set funnels upright in drying racks. Put one preweighed filter in each funnel.


3. Carefully remove the cap from PVC pipe. Pour sample into correspondingly marked filter, swirling PVC trap occasionally to suspend sediments. Rinse trap with fresh water to wash any remaining sediments into filter.


4. Allow sediments in filter to drain. Carefully rinse drained sediments in filter with fresh water to remove any salts that may add to dry weight.


5. Let samples dry for 10 days to several weeks until a constant weight is achieved (i.e. reweighing the sediments over several days producing the same results). Each sample is then weighted over 3 different days and the results will be averaged to 0.01 grams.


6. If desired, sediments may be analyzed for grain size.


Brown, Eric, 1999. PhD dissertation, to be published. University of Hawaii.

Gardner, W.D., 1980. Field assessment of sediment traps. Jour. Mar. Res. 38:40-52.

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