NYC Resources311Office of the Mayor

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
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
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)

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