2- Phytoplankton Sampling

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1 2- Phytoplankton Sampling Safety Instructions for Field Sampling All participants in the field trip must be able to swim. Non-swimmers or students otherwise handicapped or unable to swim cannot go out. Students are expected to sign a liability waiver prior to the field trip. All participants are expected to be familiar with the following safety regulations: All students aboard have to wear life preservers all the time. Wear solid shoes with rubber sole for safety reasons; no open shoes, no flip-flops or other loose shoes, no leather sole, no bare feet aboard Be aware that waves might come into the boat; so ware cloths that can get wet. Bring sun glasses and a hat to protect your eyes and brain from the sun Bring at least one quart of water (only water counts, no juice or soda!) Operate any equipment only if you are familiar with the equipment and only after the skipper has explicitly allowed deploying equipment (otherwise lines are easily entangled in the prop, destroying the prop and leaving us rowing back home). Prior to deploying any equipment overboard, make sure lines are secured to the boat to prevent loss of equipment. If interested, you might bring your photo camera and/or binocular. But make sure you have watertight storage for them. Phytoplankton Sampling There is no single, generic sampling method, you should choose a method based on your question, the precision required and your budget. Plankton is not distributed uniformly throughout the water, but has a patchy distribution in both space (vertical and horizontal) and time (between day and night, winter and summer). This means, for example, that sampling with a particular size of mesh, or during the night, or during the ebb tide will influence the results and the interpretation. When to sample Phytoplankton It is best to sample at particular time each day. Between 8.30 and a.m. is the preferred time. This is because the algae move up in the water to the surface, towards the sunlight, in the morning. In the afternoon the blue-green algae tend to sink to lower regions. By sampling at roughly the same time on each sampling occasion you can directly compare the algal results from different days. Methodology How do we collect phytoplankton? Sampling Procedures There are various methods for collecting samples for phytoplankton analysis, depending on whether a quantitative or qualitative analysis is desired. Irrespective of methods, samples should be preserved soon after collection and where possible, live samples should also be examined. 1. Surface water samples are collected by dipping a well-rinsed bucket or bottle over the side of the boat, let it fill half with water and bring it back into the boat. Fill the provided sample bottles. Standard sampling depths for "surface" water samples are 0.1 m and 0.5 m. 1

2. Water sampling bottles at discrete depths The sampling bottles or water samplers with closing mechanisms are commonly used for obtaining

Examples of gear: Nansen, Nisken, Van Dorn, Kimmerer or simply by homemade weighting bottle This method is used mainly for collecting small

The sterile bottles should be preferred.

The plankton are then concentrated by allowing them to settle, centrifuging or fine filtration. Advantages a.

Can determine detailed vertical profiles if take samples at different depths d. Quantitative (can sample known volume) Disadvantages a.

Samples often need to be concentrated for counting (settling) Procedure Lower the water sampler while in an open state to the desired sampling

2 2. Water sampling bottles at discrete depths The sampling bottles or water samplers with closing mechanisms are commonly used for obtaining samples from the desired depths. Examples of gear: Nansen, Nisken, Van Dorn, Kimmerer or simply by homemade weighting bottle This method is used mainly for collecting small forms of plankton. The water is collected at the sampling site in bottles or water samplers of 5 to 20 litre capacity. The sterile bottles should be preferred. While collecting the water samples, there should be minimum disturbance of water to prevent avoidance reaction by plankton. The plankton are then concentrated by allowing them to settle, centrifuging or fine filtration. Advantages a. it is easy to operate and sampling depths are accurately known. b. Collects all phytoplankton (including nanoplankton) c. Can determine detailed vertical profiles if take samples at different depths d. Quantitative (can sample known volume) Disadvantages a. Need many samples to get a vertical profile b. May miss phytoplankton in between sampling points c. Samples often need to be concentrated for counting (settling) Procedure Lower the water sampler while in an open state to the desired sampling depth, then release the messenger weight. The messenger weight will falls down inside on sliding rail and hit the release mechanism of the water sampler, which will close on both sides. By this way, the water together with the planktonic organisms of the specified column is trapped inside. Pull the sampler back into the boat, fill your sample in a 1 L polycarbonate sampling bottle and store the bottle in the closed cooler. Kemmerer Water Sampler Van Dorn Sampler Niskin Bottles Nansen Bottle 2

3 Meyers water sampler (Weighting bottle) is consist of an ordinary glass bottles of about 1-2 liter capacity and is enclosed with a metal band. It is weighted below with a lead weight and there are one or sometimes two strong nylon graduated ropes (o ne tied to the neck of the bottle and the other to the cork). While operation, stopper the weighted bottle, then lower it into the water. When the desired sampling depth is reached, tug the cord on the cork to pull it out of the bottle to allow water flows into the bottles. Note that this may be hard to do, as water pressure will be acting on the cork. Afterwards, using the neck rope, the bottle containing the water sample is taken out of the water columns. Up to a depth of only 20m, this type of water samples could be used. 3. Integrated water column sampling Integrated samples are usually taken from the surface to 10 m depth. The entire sample is then released into a clean bucket repeated up to three times and a 100 ml sub-sample is then removed from the bucket and preserved for later analysis e.g. phytoplankton identification. Examples of gear: Coliwasa (column integrated water sample), hosepipe sampler, pump and tube Advantages a. Collects all phytoplankton (including nanoplankton) b. Collects phytoplankton from all depths c. Quantitative (sample known volume) d. Need fewer samples to represent phytoplankton at many depths Disadvantages a. Lose vertical resolution b. Often only can sample top 10 m at most with this method c. Samples often need to be concentrated for counting 3

Coliwasa sampler (column integrated water sampler) Operation 1 Insert sampler into the water while the handle is pushed up to plug the end of the tube.

Pull up handle to re-plug the tube and remove sampler Operation 2 Insert sampler into the water while the handle is pushed down to plug the end of the tube.

4 Coliwasa sampler (column integrated water sampler) Operation 1 Insert sampler into the water while the handle is pushed up to plug the end of the tube.. At the required depth push down the handle to unplug the end of the tube allowing the liquid to enter the sampler. Pull up handle to re-plug the tube and remove sampler Operation 2 Insert sampler into the water while the handle is pushed down to plug the end of the tube. At the required depth pull up the handle to unplug the end of the tube allowing the liquid to enter the sampler. Push down the handle to re-plug the tube and remove sampler Hosepipe sampler A hose-pipe sampler is a weighted tube, 2 5 cm diameter and 4-5 m long but can be varied in length to suit the size of the water body being sampled. Weight the house at one end and attach a string to that end. Drop vertically into the water, with both end open. Then cork the top end when the tube is full of water and use the string to pull the lower end up and out of the water. Pull the crocked hose-pipe completely out of the water, and empty its contents into a bucket. This water sample taken over 1 or 2 or 5 meters is mixed well in bucket an then a subsample of 500 ml or 1 liter is taken as an integrated-water-column sample. 4

5 Plankton pumps Plankton pumps are integrating samplers that pump a continuous stream of water to the surface and the phytoplankton can then be rapidly concentrated by continuous filtration. Because the pumps can collect continuously as the tube is lowered through the water column the samples are integrated from surface to desired depth. The gear is normally used on board the vessel/boat. The sampling can also be carried out from a pier. In this method, the inlet pipe is lowered into the water and the outlet pipe is connected to a net of suitable mesh size. The net is particularly submerged in a tank of a known volume. This prevents damage to the organisms. The plankton is filtered through the net. A meter scale on the pump records the volume of water filtered. This method is used for quantitative estimation and to study the small scale distribution of plankton. This method has its disadvantages, however e.g., the frictional resistance of the sampled water in the hose can cause turbulence; breaking up colonies, breaking of large setae, and breaking into pieces long pinnate cells.. The advantage of the method is that the volume of the water pumped is known. Again the continuous sampling is possible. However, the sampling depth is limited to a few meters and it is difficult to obtain samples from deeper layers. Figure A simple on-deck pumping system for plankton sampling showing some of the components. 5

6 4. Phytoplankton nets Plankton nets are widely used for sampling phytoplankton. Gear: fine meshed (using a 5, 10 or 20 μm) phytoplankton nets Advantages a. large volumes of water can be filtered to concentrate the organisms b. Concentrates rarer cells. c. Concentrates large algae, so often settling isn t needed to identify samples d. Easily deployed from shore (tossing) or boats Disadvantages a. A large percentage of phytoplankton is small enough to pass through even the finest mesh nets. Others are burst or disintegrate when stressed or coming in contact with the net. Thus this method does not allow for accurate counting of algal species. Consequently, a plankton tow is regarded as a qualitative measure. b. The volume of water passing through the net is hard to measure exactly it s hard to get good flow meter reading and net clogs, changing efficiency so is not possible to get a quantitative measure. c. Force of towing can break up and destroy some larger algae d. Once the standard for phytoplankton collection (before 1950), phytoplankton nets are rarely used now except to collect net plankton for demonstration purposes or to isolate for culturing (not the best method for that either due to cell damage) 6

7 Different types of nets have been designed for collecting plankton of which the most commonly used one is the standard net (Fig. ). It consists of a cone shaped gauze bag equipped with a metal or plastic ring at the wider end and closed at the narrow end by a detachable plankton collecting vessel. The net mouth is attached to the towing line by usually three rope bridles from the mouth ring. A weight is attached to the end of the towing cable. The ratio of net length to net mouth diameter should be between 3:1 and 5:1. The front and tail parts of the net are reinforced with non porous textile cuffs. The gauzes used in nets are made of different materials such as bolting silk, polyester, nylon etc. Sampling with small (mouth diameter 15 cm; length 110 cm) fine mesh (5 or 10 μm) monofilament nylon nets has proved to be very successful in retaining high quality of phytoplankton. Making a Plankton tow Because most of the plankton are microscopic, they must be strained from the water with a funnel-shaped net ( Fig. ) of fine mesh (bolting silk or nylon). The nets are towed behind a moving. The plankton are funneled into a collection bucket or bottle, from which the concentrated population can be retrieved for study. Procedure 1. Ensure rope is securely fastened at the plankton net opening and that the dead end is tied to the boat. 2. At the designated site, deploy the net while the boat is underway. Do not lower the net until you instructed to do so. Lower the collecting vessel end first, paying out the tow line slowly as the net moves away from the boat. 3. Net hauls may be made at the surface or at any desired depth. If the sample is to be taken at some depth beneath the surface, a depressor weight may be attached to the towing line in front of the net. 4. The plankton net will be towed by slowly moving the boat in circles, or in a horizontal direction at depth 0.5-1m bellow the surface in order to account for horizontal patchiness of algal species. 5. Generally the towing speed should not exceed 1 ms 1 (2 knots). When nets with fine meshes (less than 20 μm) are used, speed even below 0.3 ms 1 (0.5 knot) is advisable in order to reduce clogging to minimum. 6. Record the following information in your journal or on plankton report forms: date, location (station number), tow sample number, diameter of net, mesh size of net, start time of two, and vessel or current speed. Write the same information on a sample label for the collection bottle. 7. Watch the net at all times and inform the skipper immediately if the net comes close to the boat props. 8. At the end of the tow, pull the net back into the boat. Keep the mouth of the net up, and the collection vessel end down. Record the end time of tow in your notebook. 9. Gently wash down the outside of the net with seawater. This action flushes any plankton stuck in the netting into the sample bottle. 10. Remove the plankton collection vessel (or open its end) and empty the plankton into a sample bottle. The collection may be preserved for later analysis. 11. Wash the net without the collection vessel end 2-3 times by dipping into the water. Also wash the end sample bottle and re-attach it to the end of the net for the next deployment. 12. Analyze the sample. 7

8 A vertical net tow can be also obtained by plankton net by lowering standard plankton net to the desired depth and towing it gently in a vertical direction throughout the water column to make vertical tow. How Much Plankton is in a Cubic Meter of the Sea? The amount of plankton in a sample doesn t mean much unless you consider the volume of water that you filter with the plankton net to get those plankters. Total volume of water filtered A plankton net with a circular mouth filters a volume of water approximately equal to a cylinder whose length is the tow distance and whose radius is the radius of the net (Fig. ). To compute the number of cubic meters of seawater that have been sampled by the plankton net, we use the following general formula for the volume of a cylinder: V = π r 2 L V = volume in cubic meters (m 3 ) of seawater π (pi) = r 2 = radius of net opening (in m), squared L = Length (distance net was towed, in m) The last measurement can be determined from the time of the tow and the vessel speed (see be low). Clogging of the nets introduces an error in this calculation, however, and since clogging increases with the volume of water filtered the use of nets with flow meters is strongly recommended. The determination of the volume of water filtered through any plankton net is essential for the estimation of the standing crop and for calculating the abundance of each planktonic organism (especially zooplankton) in a cubic meter (m 3 ) of seawater. Fig. A plankton net with a circular mouth filters a cylinder of water. Determination of the volume of the cylinder reveals the quantity of water filtered. Note for net samples taken by boat: When nets are towed behind a vessel, L (length of tow in meters) is calculated by knowing the speed of the vessel in meters per hour, and the time (or duration; the decimal fraction of an hour that the net was fishing). Length is calculated by the formula: Length or distance of tow = Boat speed Time. Since most vessels have speed measured in knots (nautical miles per hour), you first need to multiply by 1852 meters per nautical mile Speed in knots to find the speed in meters per hour. If the time (duration) was measured in minutes, you must divide minutes by 60 min/hr to convert the time to hours. 8

9 Example A 0.5 m diameter plankton net is towed for 15 minutes at a vessel speed of 2 knots. Calculate the total volume of water filtered. One knot is 1 nautical mile/h; there are 1850 m in a nautical mile. Solution The speed in meters per hour = = 3704 meters/hour Time in hours = 15/60 = 0.25 h Length or distance of tow = Boat speed Time. = 3704 m/h 0.25 h = 926 m V = π r 2 L V = (0.25 m) 2 (926 m) V = m 3 [volume of water filtered] Solve the following problems Problem 1: Plankton Net with 153 micron mesh: Net diameter = 50 cm (0.5 m). Duration of the plankton tow: 5 minutes, Boat speed: 5 meters in 3 seconds. Calculate the volume of water filtered Answer Distance of net tow = Boat speed x minutes towed (Speed = 5m/ 3 sec or 100 m per minute ) Distance of net tow = 100m/ min. x 5 min. = 500 meters Volume of Water Filtered by Net in Cubic Meters ( radius of net = 0.25 m) V = area of net opening x distance it was towed V = π x r 2 x distance of tow V = 3.14 x 0.25 m x 0.25 m x 500 m V = 98 cubic meters of water filtered Problem 2: Plankton net diameter = 30 cm (0.3 m). Net was towed along pier a distance of 50 meters. Calculate the volume of water filtered Answer Volume of Water Filtered by Net in Cubic Meters ( radius of net = 0.25 m) V = area of net opening x distance it was towed V = π x r 2 x distance of tow V = 3.14 x 0.15 m x 0.15 m x 50 m 9

10 Characteristics of sampling bottle A sampling bottle should meet the following requirements, some of which depend on the duration of the storage of the sample: The bottle must be clean and easily be cleaned. The bottle must not be permeable to the preservative used. The combination of bottle and screw cap should ensure a closure that is watertight (to facilitate homogenization) and almost gastight (to minimize evaporation) to allow long periods of storage. The bottle should be transparent. If kept in transparent bottles the sample can easily be examined with respect to the state of preservation and the presence of aggregates. The neck of the bottle must be wide enough. Bottles should not be filled completely with sampling water to facilitate homogenization (preferably fill to around 80 %). Labeling Soon after the sample is collected the bottles must be clearly labeled with a water proof pen. All types of information regarding plankton collection should be written on the labels so that, the plankton samples can be identified accurately. The label should contain enough information about the sample collected in order to assure proper identification of the sample. The label is written with a light colored water proof marker or wax pencil. Sample Storage and Delivery All sample containers will be stored in an insulated cooler on ice immediately after collection to maintain them at a temperature of approximately 4 C until delivery to the laboratory. 10

Standard Operating Procedure for Zooplankton Sample Collection and Preservation

Standard Operating Procedure for Zooplankton Sample Collection and Preservation Grace Analytical Lab 536 South Clark Street 10th Floor Chicago, IL 60605 April 13, 1994 Standard Operating Procedure for