Brenchley, J., & Probert, R. 1997 Aspects of the biology of Zostera in the Fleet.

Not directly relevant - primarily concerns investigations into the seed biology of Zostera populations in their natural habitat. Comment that in the Fleet, previous reports have listed two species of Zostera: Z. noltii and Z. angustifolia. Molecular investigation as part of this study indicated that Z. angustifolia is an environmentally induced phenotypic morph of Z. marina, and therefore the Fleet population should be referred to as consisting of Zostera marina only. It was noted that the Z. angustifolia morph plants tended to occur on shallow banks (higher light regime, higher temperatures), whilst those more typical of Zostera marina were found in deeper channels. The work concentrated around Langton Hive Point.

Water temperature at the sediment/water interface was measured continuously from April >96 to July >97 (data logger). <5EC in winter to >20EC in summer, fluctuating diurnally, but less than seasonal variation.

Salinity of subsurface water was measured at roughly monthly intervals. Higher in summer (~35ppt) than winter (~25 ppt).

Decreasing biomass in winter months - min. in March with near bare sediment surface. Seeds require cold stratification to germinate (8 weeks at #6EC), and will then germinate when temperatures are between 6 and 11EC - not higher. Salinity levels (equivalent to those observed) had no significant effect on germination in the laboratory. Seed germination was considerably faster with higher % germination achieved under anaerobic conditions than aerobic, in the laboratory. Field measurements confirmed that surface sediment was totally depleted in oxygen. Zostera marina seeds were found to be intolerant to drying, with best storage conditions found to be in the hydrated state in anaerobic conditions at a salinity of 30ppt at 2EC.

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