Characterization of algal community composition and structure from the nearshore environment, Lake Tahoe (United States)

Abstract

Periphyton assemblages from the nearshore environment of the west (California) side of Lake Tahoe, were analyzed to determine their taxonomic composition and community structure across habitats and seasons. Lake Tahoe is the second deepest lake in the US and an iconic oligotrophic subalpine lake with remarkable transparency. It has experienced offshore cultural eutrophication since the 1960s with observations of nuisance nearshore algal growth since the mid 2000s attributed to anthropogenic stressors. Samplings from November 2019–September 2020 provide useful snapshots against which older monitoring may be contextualized. A voucher flora, complete with descriptions, photo-documentation and referencing to species concepts employed, was created as a method of providing reproducible identification and enumeration of algal species, and more seamless reconciliation of detailed taxonomic data with future monitoring projects. The eulittoral zone (0–2 m) is seasonally dominated by elongate araphid (Synedra, Ulnaria) and stalked or entubed diatoms (Gomphonema, Cymbella, Encyonema). The sublittoral zone (>2 m) is dominated by a nitrogen-fixing Epithemia-cyanobacteria assemblage with less seasonal changes in dominance and composition that expanded to impinge on the 2 m depths of the eulittoral zone in the Fall. Sublittoral epipsammic samples, despite their proximity to rocks, had a very distinct diatom composition and high species dominance, similar to what was seen in the Fall eulittoral samples, with high numbers of Staurosirella chains and small biraphid diatoms. The deeper samples at 30 and 50 m contained high numbers of live Epithemia, and indicate a thriving sublittoral assemblage at these greater depths, but with less biomass. The 2019–20 data show many of the same diatom taxa observed in the 1970’s and 1980’s but with changes in species dominance. Notably, there was less of the green alga Mougeotia, when compared to the 1970’s data, and a higher dominance by nitrogen fixing Epithemia in the sublittoral zone, persisting year-round. These new data show roughly double the algal species biodiversity that had been documented previously in the Lake Tahoe nearshore, and is largely attributed to the methods employed. Adopting these new methods in future monitoring efforts should improve harmonization of taxonomic data and help advance our knowledge of the contributions to nearshore cultural eutrophication.

Keeping up with the landscapes: promoting resilience in dynamic social-ecological systems

“…This is particularly true in the Lake Tahoe basin, where maintaining the clarity and ecological integrity of Lake Tahoe is of paramount importance to the resilience of the lake to future disturbances. For example, increases in fine sediments and nutrients reduce clarity, which in turn has substantial ecological and social consequences: eutrophication alters the aquatic food web structure of the lake, making it more susceptible to trophic simplification and collapse as water temperatures rise in response to climate change (e.g., Chandra et al 2005, Noble et al 2023; in addition, the ecological integrity and beauty of the lake are essential features supporting a robust resource-based economy that in turn motivates and sustains substantial conservation investments. By extension, maintaining and improving the resilience of upland forested ecosystems are integral to the well-being of Lake Tahoe and the surrounding communities, similarly based on ecological and social processes that intricately link the fate of aquatic and terrestrial ecosystems across the basin.…”

A Voucher Flora of Diatoms from Fens in the Tanana River Floodplain, Alaska

“…Observations: (Plate 5, Figs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The valves are 22.1-42.8 µm long and 5.4-6.5 µm wide, and stria density is 8-11 in 10 µm. The valve outline is lunate with a flat to slightly tumid ventral margin, moderately arched dorsal margin, and rounded apices.…”

“…This is not only more information than a list of taxa, but is also more practical than a set of circled specimens (though, when available, archives of permanent slides remain important resources) [ 9 ]. Given the expeditious development of freshwater diatom taxonomy, coupled with high degrees of endemism and species diversity, no single taxonomic reference adequately supports species-level identification of all taxa in a given project [ 13 ]. Thus, developing taxonomic reference voucher floras for localized regions becomes vital for supporting long-term records, promoting efficient verification of species richness and the assessment of diatom assemblage structure.…”

Deep learning-based semantic segmentation of remote sensing images: a review

“…With the rise and evolution of deep neural networks, deep learning (DL) has made tremendous breakthroughs in artificial intelligence fields such as CV and natural language processing (NLP) (Kitaev et al, 2022;Ru et al, 2022;Zhang et al, 2022b;Noble et al, 2023). However, there are huge challenges for RS data, such as top-down data acquisition perspective, large image scale, different image resolution, and variable lighting conditions.…”