MOOS: MBARI Ocean Observing System

Introduction

The importance of time series for studies of physical oceanography is well documented and these time series allowed investigators to resolve important environmental fluctuations. Biological and chemical oceanographers are now looking to continuous observations so they can also determine the spectrum of variability and, when taken concurrently with the physical and meteorological observations, determine the relation to climate and ocean variability. The paucity of biological and chemical time series has been due, in part, to lack of instrumentation; however, increased effort has recently been placed on the development of chemical and bio-optical instrumentation for the collection of these time series.

     
Figure 1. Time series depth contour of daily temperature from the M1 mooring for 1997-99.  The El Nino signal is unmistakable in the latter half of 1997.   Similarly the La Nina signal is evident in the winter of 1998-1999.

Realizing that advances in ocean sciences are limited by the lack of instrumentation and systems capable of collecting these time series, MBARI has established a vigorous developmental program geared at making these observations possible. Spatial coverage will ultimately come from observations made from space, but high-frequency temporal and vertical coverage will need to come from moorings and drifters with arrays of in situ sensors. One of the goals of the program has been to develop a new set of control electronics and software that would allow for the collection, storage, and telemetry of data from any of a wide range of scientific instrumentation. The controller, OASIS (Ocean Acquisition System for Interdisciplinary Science), and its deployment in moored and drifting systems, has been the focus of our research. 

                                  
Figure 2.  Mooring data was used during the 1995 Coastal Ocean Processes cruise.  Time series of surface properties from the M1 mooring show conditions at this location before, during and after the drifter deployment (cruise (dashed lines) and drifter deployment (dot-dashed lines) periods)

Additional impetus for designing such a system were the increased need for real-time environmental information, the need to easily add new instrumentation as it came forward and the need to test the new instrumentation with rapidity and in an environment that was well documented with respect to other properties. The advantages of two-way, real-time telemetry are several-fold. It allows for quality control of data so as not to lose long, expensive mooring deployments. The data is immediately available for analysis, assimilation into models, and calibration of satellite sensors. The information provided in real-time by the system can be of tactical use for shipboard experiments, especially those geared at episodic events. Finally, instruments can be accessed remotely so that sampling frequency can be modified according to needs or troubleshooting performed without retrieval.

                                    
Figure 3.  Drifters were used in the 1995 IRONEX II cruise to the equator.  For 23 days and 800 kms an OASIS drifter marked the center of a 8 by 10 km patch of water fertilized with FeSO₄ in an attempt to stimulate phytoplankton growth.  The drifter’s instrumentation (nitrate analyzer, fluorometer, oxygen and light scattering sensors) measured some changes that occurred after fertilization.  Comparison of fluorescence levels between the patch drifter and another drifter deployed outside the patch show that only populations within the iron-fertilized patch responded

Another major goal has been the development of an anti-fouling system for our high frequency bio-optical instruments.  Historically, toxic anti-foulant compounds, such as tri-butyl tin (TBT) have been used to prevent the growth of such films, with some success.  However, the toxicity of these compounds and their limited period of efficacy, led us to develop alternative methods of bio-fouling protection.  Working closely with MBARI engineers we have built a shutter system designed to reduce the effects of bio-fouling on moored spectroradiometers.

                                              
Figure 4 Spectroradiometers are suspended at 10 and 20 meters in specially built cages. These bio-optical instruments help researchers understand the relationship between light and plant growth in the sea. This spectroradiometer has been outfitted with MBARI’s shutter system which protects the optical lense from biofouling. 

Next: Methods and Materials

If you have comments regarding the Biological Ocean Group's web pages you are welcome to contact us through our group's webmaster.