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Remote Sens. 2012, 4(11), 3346-3362; doi:10.3390/rs4113346

Article

Coral Reef Surveillance: Infrared-Sensitive Video Surveillance Technology as a New Tool for Diurnal and Nocturnal Long-Term Field Observations

Markus Dirnwoeber ^1,* , Rudolf Machan ²  and Juergen Herler ¹

¹ Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria ² Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria

* Author to whom correspondence should be addressed.

Received: 19 August 2012; in revised form: 10 October 2012 / Accepted: 23 October 2012 / Published: 31 October 2012

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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Abstract: Direct field observations of fine-scaled biological processes and interactions of the benthic community of corals and associated reef organisms (e.g., feeding, reproduction, mutualistic or agonistic behavior, behavioral responses to changing abiotic factors) usually involve a disturbing intervention. Modern digital camcorders (without inflexible land-or ship-based cable connection) such as the GoPro camera enable undisturbed and unmanned, stationary close-up observations. Such observations, however, are also very time-limited (~3 h) and full 24 h-recordings throughout day and night, including nocturnal observations without artificial daylight illumination, are not possible. Herein we introduce the application of modern standard video surveillance technology with the main objective of providing a tool for monitoring coral reef or other sessile and mobile organisms for periods of 24 h and longer. This system includes nocturnal close-up observations with miniature infrared (IR)-sensitive cameras and separate high-power IR-LEDs. Integrating this easy-to-set up and portable remote-sensing equipment into coral reef research is expected to significantly advance our understanding of fine-scaled biotic processes on coral reefs. Rare events and long-lasting processes can easily be recorded, in situ-experiments can be monitored live on land, and nocturnal IR-observations reveal undisturbed behavior. The options and equipment choices in IR-sensitive surveillance technology are numerous and subject to a steadily increasing technical supply and quality at decreasing prices. Accompanied by short video examples, this report introduces a radio-transmission system for simultaneous recordings and real-time monitoring of multiple cameras with synchronized timestamps, and a surface-independent underwater-recording system.

Keywords: coral; monitoring; radio transmission; remote video; unmanned station; 24-h cycles

Supplementary Files

• Supplementary File 1:

  PDF-Document (PDF, 2290 KB)

• Supplementary File 2:

  AVI-Document (AVI, 8535 KB)

  Sample video for monitoring in situ caging experiments; obtained by the radio-transmission system in combination with the finger camera. Depth: 1 m, recording distance: 60 cm, lens focal length: 1.8 mm.

• Supplementary File 3:

  AVI-Document (AVI, 8554 KB)

  Sample video for monitoring in situ caging experiments; obtained by the direct-recording system in combination with the board camera. Depth: 1 m, recording distance: 60 cm, lens focal length: 1.8 mm.

• Supplementary File 4:

  AVI-Document (AVI, 2762 KB)

  This video shows the rare event of a coral-dwelling fish (Gobiodon histrio) darting out of its host coral (Acropora gemmifera) to eat a drifting particle (at timestamp 06:11:23). The event is repeated after timestamp 06:11:26 in slow-motion. Recorded with the direct-recording system in combination with the board camera, depth 1 m, recording distance: 11 cm, lens focal length: 2.1 mm.

• Supplementary File 5:

  AVI-Document (AVI, 12699 KB)

  Edited time-lapse video captured over 6 h, which shows that the coral crab Tetralia sp. is actively manipulating the corallivorous snail Drupella sp. This potentially mutualistic behaviour was captured by chance and only discovered after the reef surveillance system was removed, which is why the process of snail removal was not captured entirely. Recorded with the radio transmission system in combination with the finger camera, depth: 2.5 m, recording distance: 100 cm, lens focal length: 3.6 mm.

• Supplementary File 6:

  AVI-Document (AVI, 5293 KB)

  Time-lapse video of a nocturnal recording under infrared (IR) illumination. The endofauna of the coral is well recognisable because the black appearance of the crab carapace and fish eyes is highly contrasted against the white coral under IR-light. Recorded with the direct recording system in combination with the board camera, depth: 1.5 m, recording distance: 16 cm, lens focal length: 3.6 mm. Infrared illumination by 2 LEDs, power output: 300 mA, distance to object: 70 cm.

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