Aquatic Life

Bronx River Plankton Sampling

2002

As part of an effort to evaluate the potential factors that explain the absence of anadromous fish in the Bronx River, Lehman College researchers gathered data on food supply in the river system.

Methods

Shore-side Sampling

Plankton samples were taken from the shallow waters of the Bronx River at Lafayette Avenue (40°49.040'N:73°52.801'W) on the 3rd, 17th, and 24th of May and on the 3rd of June 2002. Approximately 0.866 m^3 of water was sampled during each collecting period using a handheld plankton net (mesh size 125 microns).

Mid-channel Sampling

20 March 2003
40°48.84'N:73°52.33'W to 40°48.8'N:73°53.021'W

27 March 2003
40°48.057'N:73°51.421'W to 40°48.212'N:73°50.514"W

3 April 2003
40°48.9'N:73°52.6'W: to 40°48.0'N:73°51.8'W

Plankton Sampling Sites

Mid-channel Plankton Sampling Results

Taxa	Counts
Taxa	March 20th	March 27th	April 3rd
Calanoid Copepods	3471	4827	4429
Polychaete Larvae	20	27	27
Cypris Barnacle Larvae	59	13	70
Neomysis	1
Comb Jellies	1	8
Egg Sacs	2	3

Total Number of Individuals in a 3 ml concentrated sample	3524	4878	4526
Number of Individuals in a 1 ml concentrated sample	1175	1626	1509
Concentrated Sample Volume	280	360	180
Total Volume sampled by net in m^3	208.6	177.4	178.87

Plankton Number m-3	1.6X103	3.3X103	1.5X103

Shore-side Plankton Sampling Results

Taxa	Counts
Taxa	1st week May	2nd week May	3rd week May	1st week June
Calanoid Copepods	28	24	18	69
Copepod Nauplii Larvae	94	24	62	53
Harparticoid Copepods	9	8	15	13
Harparticoid Nauplii Larvae	1		3	2
Cyclopoid Copepods				2
Rotifers	11	29	2
Nematodes	17	12	13	5
Polychaetes				22
Polychaete Larvae	11	95	49	97
Diatoms
Filamentous Type (unidentifiable)	94	58	74	45
Rhobdonema	9	1	1
Navicula	79	27	362	104
Coscinodiscus	20	11	13	20
Pleurosigma	5	4	10	7
Licmophora	1
Nitzschia	7	7		27
Melosira	28	5	246	22
Thalassiothrix	1	8	7	52
Thalassiosira		4	4
Biddulphia		2	2
Rhizosolenia			1
Asterionella japonica			1
Chaetoceros			1
Diploneis			389
Amphiprora			1354	35
Dinoflagellates
Ceratium	1	8
Protozoans
Vorticella	8	15	11
Amphipod			2
Bivalve			15	4
Gastropod				12
Hydromedusa			1
Anthomedusa	1
Foraminifera			2	1
Flatworms			1	1
Coccolithophora			1
Ostracod				1
Seasquirt Tadpole Larval Stage				1

Total Number of Individuals in a 3 ml concentrated sample	425	342	2660	595

Number of Individuals in a 1 ml concentrated sample	142	114	887	198
Concentrated Sample Volume	175ml	175ml	125ml	125ml
Total Volume sampled by net in ml	885,960	1,181,280	885,960	885,960
Plankton Number ml-3	2.8X10-2	1.7X10-2	1.3X10-1	2.8X10-2
Plankton Number m-3	2.8X104	1.7X104	1.3X105	2.8X104

Plankton Occurrence of Special Note: Dinoflagellate Bloom

During our 9 August 2002 cruise we observed that the waters just south of Lafayette Avenue began to take on a color, which could best be described as that of red wine. This color pattern was noted to continue up the river for a considerable distance. We obtained a sample for examination and determined that the waters color was due to a dinoflagellate bloom. The dinoflagellate was identified as a member of the Genus Gymnodium. Using a Sedgewick Rafter counting cell we determined that the dinoflagellate concentration at this site to be 17,000cells/mL.

On 12 August 2002 we went to Lafayette Ave to see if the bloom was still occurring. It was as observed on 9 August 2002.

On 23 August 2002 we again visited our sampling site at Lafayette Ave and found that the water had returned to is usual color. We obtained water samples and upon examination found that the dinoflagellates were still present but at a much reduced concentration of 5,000 cells/mL.

— Joseph Rachlin

Downloads

Shore-side Plankton Sampling data (Excel file, 37 KB)

Mid-channel Plankton Sampling data (Excel file, 37 KB)

Bronx River Wetlands

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