Research ArticleENVIRONMENTAL STUDIES

Use of an Autonomous Surface Vehicle reveals small-scale diel vertical migrations of zooplankton and susceptibility to light pollution under low solar irradiance

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Science Advances  10 Jan 2018:
Vol. 4, no. 1, eaap9887
DOI: 10.1126/sciadv.aap9887
  • Fig. 1 The light-climate regions of the Arctic.

    Circles of yellow (left) indicate duration of the midnight sun period (3). Circles of blue (right) indicate duration of the polar night period with illumination at winter solstice defined as polar twilight (outer), civil polar night (middle), and nautical polar night (inner).

  • Fig. 2 Volume backscattering (Sv) echograms.

    (A) Acoustic Zooplankton Fish Profiler (AZFP; ASL Environmental Science Inc.) echograms at 125 (dominated by euphausiids), 200 (dominated by chaetognaths), and 455 kHz (dominated by copepods) on 23 January. The red line (and second y axis) indicates the irradiance (μW m−2) when away from the ship. The green line indicates the median depth of the SSL at each frequency. Note that a time-varied threshold of −122 dB was applied at 455 kHz. (B) AZFP echograms at 125, 200, and 455 kHz at the beginning and at the end of each survey. The red line indicates the irradiance, and the green boxes indicate acoustic backscatter data collected in the top 50 m (A) close to the ship and (B) away from the ship. Mean Sv within each box is indicated below the echograms. (C) Responses of zooplankton to ambient versus artificial light. The RV Helmer Hanssen EK60 echogram was recorded at 120 kHz in Kongsfjorden on 9 January 2017 (left) and the AZFP echogram at 125 kHz was recorded from a small boat in Kongsfjorden on 21 January 2017 (right). Black arrows indicate when the lights were turned off and on, and mean Sv in the green boxes (calculated in the linear form) for each period is indicated by the echograms. Note that the sequence of artificial light on/off is reversed in the left and right panels, and the SSL responds accordingly with avoidance during the “Light on” period. In all echograms, black areas mask the near-field region, noise, and areas below the seafloor.

  • Fig. 3 Modeled depth of a constant light level (isolume) set to be the depth limit of copepod light-mediated behavior in Kongsfjorden.

    Underwater spectral scalar irradiance [Eo(λ), μmol photons m−2 s−1] was weighted by the spectral response of C. finmarchicus to yield a photometric quantity of Calanus-utilized light that is shown in colored contours as a function of depth at 30-min intervals on the 23 January Jetyak deployment. White horizontal lines show the depth of an isolume at 5 × 10−8 μmol photons m−2 s−1 of Calanus-utilized light. UTC, coordinated universal time.

  • Fig. 4 Conceptual model of the behavioral response of zooplankton to natural solar light, light pollution, and lunar light.

    (A) Light escape response (vertical and horizontal arrows) from light pollution from a ship detected down to 100 m and up to 180 m on each side of the ship. (B) DVM of zooplankton in response to natural ambient light during the polar night. Centered around noon, organisms perform a DVM with a amplitude of 8 m within the upper 20 m of the water column. (C) In response to lunar light, zooplankton and fish perform DVM but at different depths depending on the moon phase.

  • Table 1 Details of the ASV deployments.

    Time is local time (GMT + 1 hour).

    DateNumber of transectsDurationStart timeEnd timePlatformDistance (km)
    21 January 2016200:4710:4211:29ASV Jetyak4.5
    22 January 20162103:3009:2212:52ASV Jetyak23.9
    23 January 20162303:4509:1012:55ASV Jetyak26.2
    09 January 2017101:3612:4414:20Helmer Hanssen0
    21 January 2017100:1417:3617:50Polarcirkel0
    Sum09:5054.7

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/eaap9887/DC1

    fig. S1. Map of the study area in Kongsfjorden.

    fig. S2. AZFP echograms from ASV.

    fig. S3. EK60 echograms from RV Helmer Hanssen.

    fig. S4. Vertical distribution of zooplankton.

    table S1. Ascent and descent rates of the SSL at 455 kHz in January 2016.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Map of the study area in Kongsfjorden.
    • fig. S2. AZFP echograms from ASV.
    • fig. S3. EK60 echograms from RV Helmer Hanssen.
    • fig. S4. Vertical distribution of zooplankton.
    • table S1. Ascent and descent rates of the SSL at 455 kHz in January 2016.

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