Journal article Open Access

Cabled ocean observatory data reveal food supply mechanisms to a cold-water coral reef

van Engeland, Tom; Godø, Olav Rune; Johnsen, Espen; Duineveld, Gerard C. A.; van Oevelen, Dick


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{
  "DOI": "10.1016/j.pocean.2019.01.007", 
  "author": [
    {
      "family": "van Engeland, Tom"
    }, 
    {
      "family": "God\u00f8, Olav Rune"
    }, 
    {
      "family": "Johnsen, Espen"
    }, 
    {
      "family": "Duineveld, Gerard C. A."
    }, 
    {
      "family": "van Oevelen, Dick"
    }
  ], 
  "issued": {
    "date-parts": [
      [
        2019, 
        2, 
        6
      ]
    ]
  }, 
  "abstract": "<p>Abstract<br>\nWe investigated food supply mechanisms to a cold-water coral (CWC) reef at 260 m depth on the<br>\nNorwegian continental shelf using data from a cabled ocean observatory equipped with Acoustic<br>\nDoppler Current Profilers (ADCPs), an echosounder, and sensors for chlorophyll, turbidity and<br>\nhydrography in the benthic boundary layer (BBL). Tidal currents of up to tens of cm s-1 dominated<br>\nBBL hydrodynamics while residual currents were weak (~10 cm s-1), emphasizing a supply and high<br>\nretention of locally produced phytodetritus within the trough. A direct connection between the reefs<br>\nand surface organic matter (OM) was established by turbulent mixing and passive particle settling, but<br>\nrelative contributions varied seasonally. Fresh OM from a spring-bloom was quickly mixed into the<br>\nBBL, but temperature stratification in summer reduced the surface-to-bottom connectivity and reduced<br>\nthe phytodetritus supply. A qualitative comparison among acoustic backscatter in the ADCPs (600<br>\nkHz, 190 kHz) and echosounder (70 kHz) suggests that vertically migrating zooplankton may present<br>\nan alternative food source in summer. Nocturnal feeding by zooplankton in the upper water column<br>\nsustains downward OM transport independent from water column mixing and may dominate as food<br>\nsupply pathway over sedimentation of the phytodetritus, especially during stratified conditions. In<br>\naddition, it could present a concentrating mechanism for nutritional components as compensation for<br>\nthe deteriorating phytodetritus quality. Overall, the observed patterns suggest seasonal changes in the<br>\nfood supply pathways to the reef communities. The moderating role of temperature stratification in<br>\nphytodetritus transport suggests stronger dependence of the cold-water corals on zooplankton for their<br>\ndietary requirements with increased stratification under future climate scenarios. This study<br>\ndemonstrates the added value of permanent ocean observatories to research based on dedicated<br>\ncampaigns and regular monitoring.</p>", 
  "title": "Cabled ocean observatory data reveal food supply mechanisms to a cold-water coral reef", 
  "type": "article-journal", 
  "id": "2558111"
}
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