Littoral zone production of oligotrophic lakes

Abstract

Littoral zone primary production can be expressed as the summation of the integral production of its phytoplanton and benthic components:

$$littoral prod.(mgC \cdot {m^{ - 1}}tim{e^{ - 1}}) = \mathop \smallint \limits_0^z \mathop \smallint \limits_0^x phyto prod, dzdx + \mathop \smallint \limits_0 benthic prod. dx.$$

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This expression represents a ‘wedge’ of the littoral zone, 1 m wide, extending from the shore a distance, x, to where the depth of the water, z, is equal to the maximum depth of the littoral zone (i.e. 1% of surface light intensity). The periphyton community contributed 63% of the total littoral production (0–60 m) in Lake Tahoe at a site where the benthic substratum was rock.

Evaluation of littoral productivity on a water column basis (i.e. m^-2 of lake surface) illustrated that periphyton contributed varying amounts to the total productivity depending upon the depth of the water column, the time of year, the degree bottom of slope, and the benthic substratum type. Periphyton (epilithic) contributed its maximum to 2, 8 and 16 m littoral water column productivity at Lake Tahoe during the spring (>84%) and its minimum during the summer and winter (>60%). A survey of five oligotrophic lakes indicated that periphyton often contributed the majority of the littoral zone production when the substrata were rocks or organic sediments.