Factors affecting water clarity in Lake Ellesmere, New Zealand

Abstract

Factors affecting the optical properties and water clarity of Lake Ellesmere were investigated over an 18-month period. The dominant cause of light attenuation was scattering. Clarity was found to be more dependent on very high levels of inorganic suspensoids than on phytoplankton biomass; however, high levels of chlorophyll a were also present. Fluctuations in inorganic suspensoid levels could be explained by different wind velocities before sampling. Wind velocity is thus one of several parameters that could be used to monitor the degree of light attenuation in this lake. The very compressed euphotic zone explained why macrophyte growth was restricted to shallow and/or sheltered embayments.

Optical characteristics of shallow lakes from the Pampa and Patagonia regions of Argentina

“…Sd: Jeppesen et al, 1990;Bachmann et al, 1999;Jackson, 2003;Havens, 2003;Hargeby et al, 2007;Ibelings et al, 2007;t n : Bayley and Prather, 2003;Jackson, 2003;Meding and Jackson, 2003). However, the direct measurement of broadband (PAR), or better yet the spectral diffuse vertical light attenuation, are much more precise ways of describing underwater light availability, and could therefore improve our ability to understand the conditions that regulate macrophyte vs. phytoplankton dominance, as well as other important management issues (Gerveaux and Ward, 1991;Lowe et al, 2001). Clearly all optical variables are inter-related, but they characterize different properties of the underwater light field.…”

Changes in trophic linkages to shortfin eels (Anguilla australis) since the collapse of submerged macrophytes in Lake Ellesmere, New Zealand

“…Phytoplankton productivity in the lake is high, comprised mainly of cyanobacteria (commonly Microcystis minutissima) and Chlorophyta, although large cyanobacterial blooms have not been recorded for the lake because of its high turbidity, and is generally recognized to be light limited (Lineham, 1983). There is limited submerged or emergent vegetation because of high turbidity associated with algal blooms and sediment resuspension (Gerbeaux & Ward, 1991;Gerbeaux, 1993;Glova & Sagar, 2000).…”

“…The absence of any significant re-growth of macrophytes is thought to be related to insufficient periods of clear water for establishment and canopy development of plants. Light penetration is mainly controlled by suspended sediment concentrations and to a lesser extent phytoplankton biomass (Gerbeaux & Ward, 1991). As lake levels are currently held lower than historic levels to prevent flooding of adjacent farmland and urban centres, there is frequent resuspension of shallow lake-bottom sediments (Gerbeaux, 1993).…”

Growth, survival, and recruitment of juvenile shortfinned eels (Anguilla australis)in a large New Zealand coastal lake

“…It seems unlikely that these changes in water quality will have direct effects on eel foraging behaviour and growth rates. Eels do not depend upon vision for feeding and therefore the lake's high turbidity (Secchi disc 0.11m, 66-676 g nr 3 suspended solids, Gerbeaux & Ward 1991), is unlikely to restrict effective foraging. Although the lake is eutrophic, oxygen levels are not depleted (Vant 1987) and toxic blooms of the blue-green algae, Nodularia spumigena, are rare (Taylor 1996).…”