Microbiology and biochemistry of placer rich beach sediment: Short-term response to small scale simulated mining

Abstract

In order to understand the influence of sand mining on the bacterial community of a placer rich beach ecosystem, a mechanical disturbance was simulated in Kalbadevi beach, Ratnagiri. Core samples from dune, berm, high tide, mid tide and low tide were examined for changes in the distribution of bacterial abundance and biochemical parameters up to a depth of 40cm. Average core values (n = 4/core) are examined in this study before and after disturbance. With disturbance, the bacterial abundance decreased from 10 sup(6) cells.g sup(-1) dry sediment by an order. Both direct aerobic and anaerobic viability marginally decreased. Retrievable counts on 0.01% and 0.001% strength nutrient broth in seawater agar showed 23% and 71% increase immediately after disturbance. The proteins, carbohydrates and lipids, which are the constituents of labile organic matter, did not vary significantly. The changes in these levels of the biochemical are marked only at berm and dune and masked at the other three levels by the tidal influence. ATP an index for living biomass was reduced drastically. Thus, the short-term effect showed that the simulated disturbance had a mixed effect on the microbiology and biochemistry of the sediments. It reduced total bacterial counts, total viable counts, and ATP with little effect on concentration of biochemical parameters. However, simulated mining improved the retrievability of bacteria by an order.