Bisley Watershed 3 and Quebrada Prieta Algae Monitoring



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The LTER is conducting annual monitoring of Algae, Chlorophyll a, benthic organic matter, and benthic inorganic matter in order to document baseline stream characteristics. These data may be used to examine effects of disturbances such as hurricanes on stream ecosystems.

Our long-term data shows how algal primary producers respond to disturbance.  The resistance and resilience of primary producer biomass to different types of disturbance (drought and high discharge) is affected by the relative degree of top-down control by different stream macroconsumer assemblages representative of low-order streams draining LUQ.   The LUQ  stream algae dataset is unique among LTER sites because of its long-term nature and because it provides integrated quantitative measures of algal standing crop (AFDM, chlorophyll a) at a relatively large scale (1 km stream reaches) and is not just ‘snapshot’ sampling at one location.  We also sample 2 x per year with more intensive sampling  during droughts (5-6 x per year).

We found dramatically lower levels of algal standing crop during peak drought conditions in 2015.  In Prieta, algal standing crop was 16-22 fold lower in pools and 11 -18 fold lower in riffles, compared to the long-term summer average - - - assumedly due to concentrated grazing of large numbers of omnivorous shrimps in a small volume of water. In Bisley-3, algal standing crop was 5-9 fold lower in pools and 2-6 fold lower in riffles compared to the long-term (2003-14) summer average.  Inorganic sediments in pools were highly variable and ~2 fold greater in riffles compared to the long-term summer average.

We also measured extremely high spatial variability in conductivity and solute chemistry between pools in Prieta and Bisley-3 in July- August 2015 due to the lack of flow in riffles connecting pools.  Conductivity in both streams was 1.5 - 1.6 fold greater than mean conductivity over the last decade (2002-12).

Date Range: 
2003-06-01 00:00:00 to 2016-07-31 00:00:00



Additional Project roles: 

Name: Miguel C Leon Role: Data Manager
Name: Effie A. Greathouse Role: Associated Researcher
Name: Katherine Smith Role: Associated Researcher


Field Methods: We sampled 5 pools and 5 riffles in each stream. In each pool and in each riffle, we took 6 haphazardly chosen epilithic samples using a suction device modified from Loeb (1981, An in situ method for measuring the primary productivity and standing crop of the epilithic periphyton community in lentic systems. Limnology and Oceanography 26:394-399). The 6 samples were composited into a nalgene bottle for later analysis. We thus had a single composited sample for each pool and each riffle. Bottles were brought back to the laboratory on ice. Data were collected twice per year (Spring~January and Summer ~June to August) from January 2002 to present. Loeb samples in pools were from rocks/boulders under water that was at least 3 inches deep. No specific depth criteria was used for riffles because they are shallow, but the sampled spot had to be deep enough for the Loeb sampler to work (i.e. the water had to be as deep as the tiny side hole of the Loeb sampler). Riffle Loeb samples were only taken where the water was actually flowing.

Lab methods: Each sample was sub-sampled for filtration onto 2 glass fiber filters. The first filter was a pre-weighed, pre-ashed filter for AFDM/inorganic matter analysis. The second filter was a pre-ashed filter for chlorophyll a analysis. Volumes filtered onto each filter were recorded as well as any volume not filtered. Three drops of 1% MgCO3 were added to the chlorophyll subsample during filtration. Chlorophyll filters were immediately frozen. AFDM/inorganic matter filters were immediately dried at 50 C for at least 24 hours. Later, chlorophyll filters were analyzed fluorometrically according to standard methods [APHA (American Public Health Association). 1985. Standard methods for the examination of water and wastewater, 16. American Public Health Association, Washington, D.C.]. The AFDM/inorganic matter filter was later weighed to the nearest 0.001 g, ashed at 500 C for 3 hours, and re-weighed to determine inorganic and ash-free dry mass (AFDM) per unit area.



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