Antarctic stream ecosystems: physiological ecology of a blue‐green algal epilithon

• Published in: Freshwater Biology
• Main Authors: VINCENT, WARWICK F., HOWARD‐WILLIAMS, CLIVE
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1986
• Subjects: Antarctic; The Antarctic; Victoria Land; McMurdo Sound; Antarc*
• Online Access: http://dx.doi.org/10.1111/j.1365-2427.1986.tb00966.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2427.1986.tb00966.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.1986.tb00966.x

SUMMARY. 1. Several dozen summer meltwater streams are located in the McMurdo Sound region (c. 78°S 165°E) of southern Victoria Land. They are characterized by a highly variable flow regime at diel, seasonal and annual times caleis; wide fluctuations in temperature and nutrient content; and a very simple epilithic community of cyanophytes ( Nostoc spp., Oscillatoriaceae), bacteria, fungi and microherbivores. 2. The epilithon survives the dark Antarctic winter as dry, frozen mats which provide a large inoculum for growth the following summer. This overwintering assemblage retains a high metabolic capacity and responds rapidly to rehydration. 3. In a series of artificial substrate experiments, biomass accumulation rates were generally less than 0.1 In units d −1 . Colonization and growth on the substrates was inversely related to the suspended sediment load of the stream. There was also a visual correspondence between per cent algal cover of the natural streambed and the clarity of the streamwater. Sloughing losses may limit community biomass, particularly in the turbid flowing waters. 4. During running water conditions the mature communities had very low gross photosynthetic rates per unit chlorophyll (<0,1 μg C (μg chl a .h) −1 and per unit carbon (<0,2 μg C (mg biomass C.h) −1 ). Respiration was generally a high percentage (up to 92%) of gross photosynthesis, which probably reflected the high population densities of microheterotrophs in the community. 5. The floristically simple epilithic mats slowly accumulate to extreme biomass levels (>20 μg chl a cm −2 , <20 mg C cm −2 ). Production rates per unit biomass are low, probably in response to the cold temperatures of the Antarctic stream environment, and the accumulated biomass represents several seasons of growth.