Biogenic silica and phosphorus accumulation in sediments as indices of eutrophication in the Laurentian Great Lakes

Biogenic silica (BSi), total phosphorus (TP), and biologically available phosphorus (AVP) were measured in short cores from Lake Michigan, Lake Erie, and Lake Ontario. Peaks in BSi concentration and peaks in BSi:TP or BSi:AVP ratios provided stratigraphic signals of water column silica (Si) depletion as a response of increased diatom production to P enrichment and decreased diatom production resulting from silica depletion. By contrast the stratigraphic record of P accumulation provided very weak signals of the historical nutrient enrichment in the water column. These results indicate that system P recycling has a higher rate constant than Si recycling and, as a consequence, that relatively small levels of P enrichment can increase diatom production and sedimentation eventually causing Si depletion and Si-limited diatom production in the water mass.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42873/1/10750_2004_Article_BF00026648.pd

Paleolimnological comparison of the Laurentian Great Lakes based on diatoms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110008/1/lno19933861311.pd

Variations in Melosira islandica valve morphology in Lake Ontario sediments related to eutrophication and silica depletion

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109796/1/lno19853020414.pd

Siliceous microfossil succession in the recent history of Green Bay, Lake Michigan

Quantitative analysis of siliceous microfossils in a 210 Pb dated core from Green Bay of Lake Michigan shows clear evidence of eutrophication, but a different pattern of population succession than observed in the main deposition basins of the Great Lakes. Sediments deposited prior to extensive European settlement ( ca A.D. 1850) contain high relative abundance of chrysophyte cysts and benthic diatoms. Quantity and composition of microfossils deposited during the pre-settlement period represented in our core is quite uniform, except for the 30–32 cm interval which contains elevated microfossil abundance and particularly high levels of attached benthic species. Total microfossil abundance and the proportion of planktonic diatoms begins to increase ca 1860 and rises very rapidly beginning ca 1915. Maximum abundance occurs in sediments deposited during the 1970's, with a secondary peak in the late 1940's — early 1950's. Increased total abundance is accompanied by increased dominance of taxa tolerant of eutrophic conditions, however indigenous oligotrophic taxa, particularly those which are most abundant during the summer, are not eliminated from the flora, as in the lower Great Lakes. It appears that a combination of silica resupply from high riverine loadings and replacement of indigenous populations by periodic intrusions of Lake Michigan water allow sequential co-existence of species usually exclusively associated with either eutrophic or oligotrophic conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43092/1/10933_2004_Article_BF00153737.pd

Wet and dry deposition of phosphorus into Lake Huron

The deposition rates for wet, dry, and integrated fallout of P to the southern portion of Lake Huron were determined. Samples were analyzed for water-soluble, acid (pH =2) soluble, and insoluble (bound) P. The term ‘available P’ was used to indicate the sum of the water- and acid-soluble fractions of P in each type of input. Of the integrated fallout samples, approximately one-third was present as available P. The deposition rate for dry fallout of available P was determined to be 1.7 ng cm −2 day −1 . The wet deposition rate was estimated to be 2.2 ng cm −2 day −1 for available P. Total fallout of available P, determined from shore-based integrated fallout collectors, was calculated to occur at a rate of 6.5 ng cm −2 day −1 . The difference between the wet-plus-dry deposition and the integrated deposition rates has been ascribed to the contamination of integrated fallout collectors by local sources (roads, agricultural activity, etc.) though attempts were made to minimize this problem. The presence of large quantities of biological material (pollen, algae, insect larvae) accounted for a large fraction of the difference observed, especially in the spring months.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43894/1/11270_2004_Article_BF00464714.pd

Quantifying measures to limit wind driven resuspension of sediments for improvement of the ecological quality in some shallow Dutch lakes

Although phosphorus loadings are considered the main pressure for most shallow lakes, wind-driven resuspension can cause additional problems for these aquatic ecosystems. We quantified the potential effectiveness of measures to reduce the contribution of resuspended sediments, resulting from wind action, to the overall light attenuation for three comparable shallow peat lakes with poor ecological status in the Netherlands: Loosdrecht, Nieuwkoop, and Reeuwijk (1.8–2.7 m depth, 1.6–2.5 km fetch). These measures are: 1. wave reducing barriers, 2. water level fluctuations, 3. capping of the sediment with sand, and 4. combinations of above. Critical shear stress of the sediments for resuspension (Vcrit), size distribution, and optical properties of the suspended material were quantified in the field (June 2009) and laboratory. Water quality monitoring data (2002–2009) showed that light attenuation by organic suspended matter in all lakes is high. Spatial modeling of the impact of these measures showed that in Lake Loosdrecht limiting wave action can have significant effects (reductions from 6% exceedance to 2% exceedance of Vcrit), whereas in Lake Nieuwkoop and Lake Reeuwijk this is less effective. The depth distribution and shape of Lake Nieuwkoop and Lake Reeuwijk limit the role of wind-driven resuspension in the total suspended matter concentration. Although the lakes are similar in general appearance (origin, size, and depth range) measures suitable to improve their ecological status differ. This calls for care when defining the programme of measures to improve the ecological status of a specific lake based on experience from other lakes.

The distribution of Heterotrissocladius oliveri Saether (Diptera: Chironomidae) in Lake Michigan

Fifty one chironomid species were identified from 504 samples collected at depths ranging 8 to 267 m in Lake Michigan, U.S.A. Heterotrissocladius oliveri Saether occurred in 32% of these samples and had an average abundance of 22 m −2 which was similar to other estimates from the Great Lakes. Maximum average lake-wide density was at 30 to 60 m (41 m −2 ). At depths ≥60 m, H. oliveri was the dominant chironomid species comprising 75% of total Chironomidae. The substrate preference of H. oliveri differed within each depth regime considered: at 30–60 m, 2–3 ϕ; at 60–120 m, 3–5 ϕ, 7–9 ϕ; and at 120–180 m, 6–8 ϕ. Abundance was notably reduced at all depths in substrates characterized as medium silt (5–6 ϕ). On a lake-wide basis, the distribution pattern suggested H. oliveri was most numerous from 30 to 60 m along the southwestern, eastern, and northern shorelines and at 60–120 m depths along the southern and eastern shorelines. Increased abundance in the South Basin was concurrent with evidence of increased sedimentation at 60 to 100 m. However, in several other areas of the lake, high densities were associated with medium to very fine sands relatively free of silts and clays. This observation suggested occurrence of H. oliveri was minimally affected by sediment type.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42871/1/10750_2004_Article_BF00008856.pd

In situ nutrient assays of periphyton growth in a lowland Costa Rican stream

Nutrient limitation of primary production was experimentally assessed using an in situ bioassay technique in the Quebrada Salto, a third-order tropical stream draining the northern foothills of the Cordillera Central in Costa Rica. Bioassays employed artificial substrata enriched with nutrients that slowly diffuse through an agar-sand matrix (Pringle & Bowers, 1984). Multiple comparisons of regression coefficients, describing chlorophyll- a accrual through time for different nutrient treatments, revealed positive micronutrient effect(s). Micronutrient treatment combinations (Fe, B, Mn, Zn, Co, Mo, EDTA), supplemented with and without nitrate and phosphate, exhibited significantly greater chlorophyll- a accrual over all other treatments (P < 0.05), supporting over three times that of the control after 14-d of substratum colonization. Neither of the major nutrients (N or P) produced a significant stimulation, although the N treatment displayed ≃50% more chlorophyll- a than the control after 14-d. Similarly, Si, EDTA, and Si + N + P treatments did not exhibit chlorophyll- a response curves that were significantly different from the control. During the experiment, mean NH 4 -N and (NO 2 + NO 3 )-N concentrations in the Salto were 2.0 µM (28.6 µg · l −1 ) and 7.2 µM (100.2 µg · l −1 ), respectively. High concentrations of PO 4 -P ( = 2.0 µM; 60.9 µg · l −1 ) and TP ( = 3.0 µM; 94.0 µg · l −1 ) were also found, and consequently low molar N:P ratios = 4.7). Despite the potential for N limitation in the system, both N and P appear to be at growth saturating levels. This may be due to micronutrient limitation and/or light limitation of periphyton growth in densely shaded upstream portions of the stream.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42872/1/10750_2004_Article_BF00008489.pd