Figure 1: Early competent sand dollar larvae do not display 'desperate' behaviors at settlement, with or without turbulence exposure. We either exposed D. excentricus larvae 10 day post fertilization (dpf) (reared at ~20\u00b0C) to 3 min of 6 W/kg turbulent shear or did not. Then, we transferred exposed and control larvae into one of two settlement conditions: 24 hrs in MFSW alone (left side of graph) or a 1 hr exposure to 40mM excess KCl in MFSW \u2013to assess competence\u2013 followed by a 24 hr recovery in MFSW. We detected an effect both of turbulence exposure (F1,12=5.36, p<0.02) and settlement medium (F1,12=228.93, p<0.001) on proportion of larvae settled, but no clear interaction (F1,12=3.41, p=0.09).
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Figure 2: Fully competent sand dollar larvae exposed to turbulence are less choosy about settlement substrate, and thus behave like 'desperate' larvae. We either exposed D.\u00a0excentricus larvae 11\u00a0dpf\u00a0(reared at ~20\u00b0C) to 3 min of 6 W/kg turbulent shear or did not (\"no turbulence\"). Then, we transferred exposed and control larvae into one of two settlement conditions: 0% extract of sand from sand dollar aquaria (MFSW; no inducer) or 40% extract of sand from sand dollar aquaria (strong natural inducer), and counted the numbers settled at 1 and 16 hrs. We also exposed a separate set of control (no turbulence) larvae for 1 hr to 40mM excess KCl in MFSW, followed by recovery in MFSW. More than 95% of these latter larvae settled, confirming that the larvae in this experiment were indeed fully competent.
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Figure 3: Fully competent sand dollar larvae exposed to turbulence are less choosy about settlement substrate, and thus behave like 'desperate' larvae. We either exposed D. excentricus larvae 40 dpf (reared at ~14\u00b0C) to 3 min of 6 W/kg turbulent shear or did not (\"no turbulence\"). Then, we transferred exposed and control larvae into one of two settlement conditions: 0% extract of sand from sand dollar aquaria (MFSW; no inducer) or 200% extract of sand from a beach without sand dollars (poor quality natural inducer), and counted the numbers settled at 1.5, 3, 7.5 and 19 hrs. We also exposed a separate set of control (no turbulence) larvae to a strong natural inducer (30% extract of sand from sand dollar aquaria; right side of graph). This treatment not only confirms that the larvae were fully competent (100% of larvae settled by 8 hrs), but indicates the expected rate of settlement response in a strong cue as a basis of comparison to the sub-optimal cues described above.
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We performed all statistical analyses using R (version 3.4.2) and the lme4 package.
These data are presented in Hodin et al (2018).
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Adult Dendraster excentricus were collected from two geographically distinct populations: 1) a subtidal population (~\u2009100\u00a0m offshore and 1.5m below the surface at mean lower low water) approximately 30m east of Municipal Pier 2 in downtown Monterey CA, USA; 2) an intertidal population on Crescent Beach in East Sound, Orcas Island, WA, USA. Adults in Monterey were collected by snorkeling\u00a0and transported to Hopkins Marine Station (\u201cHMS\u201d; Pacific Grove CA, USA). Adults in East Sound were collected at low tide\u00a0and transported to Friday Harbor Labs (\u201cFHL\u201d; Friday Harbor, WA, USA). In both locations, the sand dollars were partially buried within fine sediments (collected from the adult beds) in flowing seawater aquaria until spawning. (Hodin et al, 2018). These adults served as sources for the larvae used in the experiments.
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We raised larval sand dollars (Dendraster excentricus) through their feeding larval stage using standard methods [Strathmann, 1987 and 2014], and on various days after larvae had become competent to settle, we subjected a subset of them to a brief turbulence exposure of a specified high intensity (6 W/kg) conforming to that measured on wave-exposed rocky coasts. Immediately after exposure, we transferred the larvae into different settlement inducing media: Millipore-filtered seawater (MFSW), extracts of sand from inside or outside sand dollar beds, or excess potassium chloride in MFSW. We then quantified settlement as it relates to turbulence exposure and settlement medium. For more detail refer to Hodin et al (2018) and prior papers [Gaylord et al, 2013; Hodin et al, 2015].
BCO-DMO Processing:
\n- added conventional header with dataset name, PI name, version date, reference information
\n- renamed parameters to BCO-DMO standard
\n- replaced blank cells with '-' ('not applicable')