Date

2001

Document Type

Capstone Project

Degree Name

Bachelor of Science (B.S.)

Department

Science & Environmental Policy

Abstract

any marine organisms are highly dependent on the small-scale water current flows around reefs for many aspects of their physiological and biological processes. Because of these dependencies, many scientists are interested in studying these flows. Traditional means of measuring currents assumes water movement to be consistent over large areas and generally fails to describe patterns of flow with the high resolution needed to show movements over and around small reefs. Water movements, like many other physical attributes of the marine environment, are heterogeneous, changing dramatically over spatial and temporal scales. Experiments designed to learn about the biotic and abiotic features of these environments may benefit from simultaneously sampling multiple points within small spatial scales. This simultaneous small spatial scale (<1m) sampling returns the high-resolution data needed to describe how attributes differ from one area to adjacent areas. Obtaining or designing the instrumentation used for these studies requires some technical creativity but is only part of the challenge in acquiring data from the small spatial scales relevant to certain organisms. There are some logistical challenges to placing equipment in the field; when multiple instruments are involved the problems of anchoring them to the substrate are multiplied. Traditional methods, such as using epoxy or drilling holes to place hardware into the substrate, have been used extensively in many subtidal studies, however, concerns exist about the application of these methods in a study that involves many autonomous instruments, requiring the replication of an anchoring method mulitple times. Some of these methods damage the substrate and others are too insecure for delicate instruments. This study tests specialized hardware specifically developed for secure and low impact anchoring of sampling instruments to rock substrates. The anchoring system was constructed from easily obtained stainless steel and aluminum materials for less than $40 (US). It worked by spanning the study area with cables fastened to the reef by chocks wedged into crevices. Cables were supported over the reef by cylindrical struts that provided secure placements of equipment. The system was customized to accommodate different substrates and a multiple number of sampling instruments. The system's hardware and design were tested on granite and shale substrates in Monterey Bay, California. Testing for a total of 56 directly measuring current velocities at a third. Wave conditions measured during field tests were consistent with averaged historical conditions from years 1987-1993, suggesting that the surge conditions at depth during testing were similar to expected forces generated by currents moving at approximately .5ms⁻¹. It was found that the system worked well for the purpose of applying current measuring instruments to granite and shale substrates in depths as shallow as 9 meters, suggesting that this system is reliable when used under conditions similar to those experienced during testing.

Comments

Capstone Project (B.S.) Earth Systems Science & Policy Institute

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