Rio Mameyes diatoms in the Rio Mameyes from 1998 to 2001

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Survey expeditions of the diatoms of Puerto Rico and other Caribbean islands were conducted briefly in the late 1800's and early 1900's,. However, until now no intensive study of changes in freshwater diatom community over time has been undertaken. In conjunction with other measures of quality of water in the Rio Mameyes, i.e. pH, conductivity, temperature, nutrients, periphytic diatoms have been collected monthly for two years in an effort to detect the effects of disturbances such as hurricanes and human demands on a river ecosystem.

Date Range: 
1998-03-01 00:00:00 to 1998-05-31 00:00:00



Additional Project roles: 

Name: Eda Melendez-Colom Role: Data Manager
Name: Frederick Scatena (In Memorium) Role: Associated Researcher


Field Methods: Beginning in May 1998, monthly samples were collected from 3 sites along the Rio Mameyes. After Hurricane Georges on September 21, 1998, 2 more sites were added and samples were collected weekly for the following 10 weeks. In January 1999 monthly sampling was resumed. On each date 9 samples were collected at each site in the wide, deeper sections of the river, and 3 samples were collected from sites that were shallow and narrow. In the wide sections of river, 3 samples each were collected from the right, center, and left of the river. Each sample is represented by the scrapings of a known area of one rock (16 or 32cm2) using a template, a razorblade, a toothbrush, and deionized water to rinse the sample into a labeled bottle. Samples were collected from the same depth on each date (45 cm deep on the left and right sides of the river and 80 cm deep from the center of the river). In the shallower sections of the river samples were collected from approximately 10 cm depth. For more details see Report) Lab methods: Samples were kept cool and transferred to the lab where they were preserved with 1-2 ml of Lugol's solution and 1-2 ml of 10% formalin. After at least 8 hours to allow for settling the samples are reduced, volumes recorded, split, and transferred to 25 ml scintillation vials. Part of each sample was saved for later ash-free dry weight analysis and part was saved for enumeration and identification. Ash-free dry weight: Preparation for ash-free dry weight was performed according to Standard Methods for Wastewater Analysis. Glass-fiber filters (0.45um) were dried, burned at 450oC, and weighed. Each sample was filtered with suction using a pump. Samples were rinsed thoroughly with DI water to remove traces of formalin and Lugol's solution. (A test was conducted to see if residual Lugols or formalin was left on the samples after incineration at 450oC with and without rinsing. A significant amount of Lugols remained on samples without rinsing, but was not detected after rinsing.) The sample-laden filters were dried thoroughly for 24 hours at 105oC, weighed, burned for 6 hours at 450oC in a muffle furnace, then weighed again. The difference in weight represented the organic component of the sample, i.e. algae, bacteria, detritus. This value was converted to grams per meter2 of river substrate. Enumeration: A 1 ml aliquot of the fraction reserved for this analysis was placed in a Sedgewick-rafter counting cell. This was examined at 20X for live and dead cells. The proportion of live to dead cells seen in one vertical strip of the Sedgewick-rafter cell was recorded. In more densely crowded samples a convenient number of fields were scanned (usually 9 to 15 fields). The volume of the sample, the volume of the aliquot analyzed (the fields or the strips), the area of the substrate scraped (a fraction of the whole sample), and the number of cells counted were used to calculate the number of cells per mm2 of river substrate. Estimates of the area covered by each cell were also made. Identification: The enumerated aliquot was returned to the sample in a glass scintillation vial. The contents of the vial was then settled for at least 8 hours, reduced via siphoning, resuspended with deionized water, and resettled at least three times to remove preservatives. After the last reduction, an equal volume of nitric acid was added to the sample along with a few grains of potassium dichromate (Patrick, 1967). This was settled for at least 8 hours to dissolve the organic component of the sample and leave only the siliceous shells of diatoms. This was then diluted with DI water, settled, siphoned, and diluted again at least 5 times to return the sample to a neutral acidity. A few drops of shaken sample (not too concentrated to obscure microscopial viewing) was transferred to a #1 cover slip that had been labeled with the sample ID, and dried on a hotplate. A drop of Cargill Meltmount was melted onto a labeled microscope slide and the sample-crusted cover slip was inverted onto this drop and gently pressed flat, when necessary. Slides prepared in this way could be examined at 100x for the fine detail necessary for taxonomic identification. Approximately 900 cells were counted from each site (100-300 per slide). The number of species per number of cells counted was used to determine the diversity present at each site.


Sedgewick-rafter counting cell

Additional information: 

In: "An Annotated Survey of Common Periphytic Diatoms of the Río Mameyes, Northeast Puerto Rico". September 2001 (Report): Part A, Part B (PDF files)

Sites descriptions:

Site and Location

Elevation (Drainage area Riparian vegetation and cover Channel features Land use
Site A Within USFS research area: ~ 200 m (35 ha) Closed canopy, native tree species Tributary channel - steep gradient, boulder lined Mature forest; Limited public access
Site B At bridge crossing Rio Mameyes ~85m (1758 ha) Open canopy, native and non - native tree species Main channel - steep gradient, boulder and bedrock lined Forest Area used for swimming and picnicking
Site C Near the municipal water intake ~15 m (3460 ha) Open canopy, tall grass, native and non-native tree species Main channel - low gradient, sand and cobble bed Forested; Mixed suburban land use
Site D in golf course ~1 m (3483 ha) Open canopy, bamboo,  some wetland vegetation, golf-course grass Main channel - low gradient, sand and cobble bed, submerged aquatic vegetation, last non-tidal freshwater reach Residential, light commercial, and golf course
Site E crosses urban area and golf cours ~1 m (419 ha) Open canopy,  partially open woody vegetation and golf course grass Tributary channel - Low gradient, sand and pebble bed, some submerged aquatic vegetation Residential, light commercial, and golf course

The locations are based on locations for the chemistry data that Bill McDowell and Fred collected for years, so the river distances are the same.  The codes in the parentheses are the ones I remember from the chemistry dataset.
A = Bisley, Quebrada 3 (Q3)
B = Puente Roto (MPR)
C = the intake in Fortuna (MIN)
D = the main channel just downstream from the little tributary in the Westin Rio Mar golf course (MTC)
E = just upstream of the mouth inside the tributary in the Westin Rio Mar golf course. (MTRIB)



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