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A new species of Aulacoseira Thwaites is described from sediment deposits of Surprise Lake, an isolated lake located in the New Jersey Highlands. The species is characterized by (1) a low mantle, (2) unevenly distributed mantle areolae of variable size and shape, and (3) a valve face covered by rounded areolae. The new species is most similar to Aulacoseira biseriata (Grunow in Van Heurk) Houk, R. Klee & H. Tanaka. Both taxa possess frustules with mantles that are low, with irregular pervalvar rows or scattered areolae. However, the two species differ in the shape and pattern of the areolae, the shape and structure of the mantle wall, the shape and depth of the ringleist, and other morphological features. In this study, we present light and scanning electron microscopic images of the new species and compare it to the most similar taxa. [ABSTRACT FROM AUTHOR]

We used sediment diatoms to infer historical changes in total phosphorus (TP) concentration in 26 New York and New Jersey (USA) lakes using a top–bottom approach (i.e., the top of the core represents present conditions and the bottom represents past conditions). Detailed stratigraphic analyses were performed on cores from Greenwood (New Jersey and New York) and Cossayuna lakes (New York). TP reconstructions were performed using 2 weighted-averaging partial-least-squares (WA-PLS) transfer functions: (1) an interregional 278-lake calibration set from northeastern United States (NE-US model: r2boot= 0.69, root mean square error of prediction RMSEP) = 1.8 μg/L); and (2) a regional 33-lake (callibration set from New Jersey and New York (NJ-NY model: r2boot= 0.54, RMSEP = 1.5 μg/L). The NJ-NY model provided better estimates for modern TP but failed to provide reliable estimates for low TP values and reliable modern analogs for half of the bottom samples. Low TP concentrations were better inferred by the NE-US model, which included a higher number of oligotrophic lakes. Average change for all lakes was an increase of 2 to 7 μg/L TP. Greenwood and Cossayuna lakes inferred TP concentrations have increased up to 21 μg/L, presumably as a result of post-settlement anthropogenic activities. The inferred TP temporal changes provide important insight on the magnitude of cultural eutrophication. The use of 2 different inference models demonstrates the advantage of using a regional versus a larger-scale inference model in estimating the degree of change in historical lake TP. Careful interpretation of TP reconstructions can be used to provide reliable estimates of cost-effective targets for lake restoration programs. [ABSTRACT FROM PUBLISHER]

Predictions of the extent of forest fires under warmer and drier conditions in boreal regions require knowledge of long-term relationships between fire and climate. However, many long-term studies that utilize the remains of total charcoal in lacustrine sediments fail to demonstrate a relationship between climate change and fire activity. A new approach to reconstruct the relative-area burned based on specific types of charcoal particles (the charcoal-morphotype (CM) fire index) has shown significant correlations to recorded forest fires. Here we assess the utility of the CM derived from an analysis of charcoal morphotypes in sediment cores from Opatcho Lake (British Columbia, Canada) using two independent paleoclimate proxies over the last 400 years, and since the mid Holocene. Over the past 400 years, significant correlations between the CM fire index and independent climate reconstructions (diatom-inferred salinity, dendroclimatic reconstructions of temperature and precipitation, and reconstructions of the Pacific Decadal Oscillation) range from 0.35 to 0.42. Similarly, since the mid Holocene the correlation between the CM fire index and independent proxies of past climate (diatom-inferred salinity and temperature inferences from chironomids from the southern interior of British Columbia) range from 0.70 to 0.76. These significant correlations strongly contrast with the very low and insignificant correlations between the CM fire index and total charcoal, suggesting that this approach provides paleofire information not available from traditional techniques. The CM fire index suggests that fires were at least two- and five-fold larger than those observed during the instrumental period, over the last 400 and 6000 years, respectively. [ABSTRACT FROM AUTHOR]