Methods and mathematical approaches for modeling Cladophora glomerata and river periphyton.

摘要

Research on the filamentous green algae Cladophora glomerata has been a topic of interest for many years. However, models and experimental methods are still needed to better describe and understand the spatial distribution of Cladophora in flowing water. As a consequence, a general approach towards modeling Cladophora in rivers is first presented. The influence of fluid velocity on resource acquisition (i.e., nutrient uptake) and removal by shear stress are specifically described. Methods are tested using a 0-D point in space through time model, against a limited dataset from a small shallow river (Clark Fork) and show reasonable results and proof-of-concept. Thereafter, a 1-D approach is considered to understand the lateral distribution of benthic algae in rivers across a cross-section due to gradients in light. An analytical solution comparing zero- and first-order growth rates is described, and a numerical model is applied to several transects on a large deep river (Yellowstone River) to validate the model. Differences between Cladophora and diatoms are noted, and multiple algal state-variables are recommended to better describe algal dynamics. Methods are then described to parameterize certain components of the proposed models. Included are the use of low-cost unmanned aerial vehicles (UAVs) to characterize the spatial variability of Cladophora in flowing water (i.e., remote-sensing), and velocity mapping with an acoustic Doppler current profiler (ADCP) to assess habitat suitability and critical velocities for Cladophora establishment. Both appear useful to the study of benthic ecology and aid in identifying locations of spatial preference and optimal and threshold velocities for its formation. Finally, the attenuation of photosynthetically active radiation (PAR) in the Cladophora thallus is determined both in situ and in an experimental flow tank using a fiber-optic sensor. PAR loss within the algal mat is noted to be an important consideration in the aquatic light environment and the rate of attenuation (i.e., extinction coefficient) is explained best by the thickness of the algal biomass. The underlying cause is likely related to compression of the algal filament from oncoming water. All of the research above contributes to a fundamental understanding of Cladophora behavior in flowing waters.