Conceptual summary of the seagrass responses to hypo-salinity.

<p>High (marine, 36 PSU) salinities are “optimum”, as shoot density steadily increased throughout the experimental period at this salinity while sexual reproduction (for <i>H. ovalis</i>) was at its “peak”. At slightly depressed salinities (30–33 PSU) there appeared to be a “sub-optimal” transition zone as shoot density showed minimal increase and, furthermore, sexual reproduction (for <i>H. ovalis</i>) was low. With further hypo-salinity (<30 PSU), a stress-induced morphometric response was associated with a re-prioritisation of resources that saw massively increased shoot density (and leaf area) and reduced sexual reproduction. At extreme hypo-salinity (3–6 PSU) plant mortality occurred. The cut-off for each response phase moved to higher salinities with increased duration of exposure.