The vertical distribution of chlorophyll differed in. its pattern between September 1993 when monthly precipitation was 200-350 mm in July and August (similar to an average year) and September 1994 when it was well below the average (8-50mm). Chlorophyll was more abundant in the epilimnion in 1993, while in 1994 it was less in the mixed layer but instead showed a peak in the thermocline. Algal biomass decreased in the mixed layer due to the absence of nutrients from river water under drought conditions in September 1994. As a result, light intensity sufficient for photosynthesis could penetrate into the thermocline. Nutrients available for algae were supplied by physical and chemical processes from the hypolimnion and/or from turbid water transported from the shore-bottom into the thermocline. The subsurface chlorophyll maximum seems to have been formed by in situ growth of algae in the thermocline relatively rich in nutrients under sufficient light conditions.
MCCs are linear invaginations of the yeast plasma membrane that form stable membrane microdomains. Although over 20 proteins are localized in the MCCs, it is not well understood how these proteins coordinately maintain normal MCC function. Pil1 is a core eisosome protein and is responsible for MCC‐invaginated structures. In addition, six‐tetraspan membrane proteins (6‐Tsp) are localized in the MCCs and classified into two families, the Sur7 family and Nce102 family. To understand the coordinated function of these MCC proteins, single and multiple deletion mutants of Pil1 and 6‐Tsp were generated and their MCC structure and growth under various stresses were investigated. Genetic interaction analysis revealed that the Sur7 family and Nce102 function in stress tolerance and normal eisosome assembly, respectively, by cooperating with Pil1. To further understand the role of MCCs/eisosomes in stress tolerance, we screened for suppressor mutants using the SDS‐sensitive phenotype of pil1Δ 6‐tspΔ cells. This revealed that SDS sensitivity is caused by hyperactivation of Tor kinase complex 2 (TORC2)‐Ypk1 signaling. Interestingly, inhibition of sphingolipid metabolism, a well‐known downstream pathway of TORC2‐Ypk1 signaling, did not rescue the SDS‐sensitivity of pil1Δ 6‐tspΔ cells. These results suggest that Pil1 and 6‐Tsp cooperatively regulate TORC2 signaling during the stress response.
An intermediate layer of highly turbid water was found at the seasonal thermocline in the southern part of the North Basin of Lake Biwa during synoptic observations conducted during late August to mid-September 1993. Vertical CTD, transmissometer and nearinfrared backscatter profiles indicated that a turbid effluent from the Yasu River penetrated
As a part of the Biwako Transport Experiments (BITEX'93), we did synoptic transects covering both the South Basin and the North Basin from 24 August -13 September, 1993 every day except two stormy days (4 and 9 September). Within a few hours before noon of each day, vertical profiles were conducted for temperature, chlorophyll a fluorescence (chl-a), turbidity, and dissolved oxygen concentration (DO) every 5 cm. Temperature profiles showed the surface mixing regime varied daily, influenced by fluctuations in surface cooling and wind forcing. In the North Basin, the metalimnion was 10-15 m below the lake surface, which was deeper than the euphotic zone. Chl-a tended to peak in the middle of the epilimnion, decrease rapidly in the metalimnion and was very low in the hypolimnion.A marked turbidity maximum was observed in the metalimnion after heavy discharge of turbid water from rivers. A pronounced feature was the metalimnetic DO minimum layer, which developed during warm and calm weather. Immediately after cool and windy weather, this layer became obscure, associated with a DO decrease in the epilimnion. This implies that the low DO water in the metalimnion was mixed into the upper layer due to the strong vertical mixing.
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