Photosynthetic light requirements and vertical distribution of macroalgae in newly ice-free areas in Potter Cove, South Shetland Islands, Antarctica

DOLORES DEREGIBUS; MARIA LILIANA QUARTINO; GABRIELA LAURA CAMPANA; FERNANDO ROBERTO MOMO

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2016 p. 153 - 166

0722-4060

In Potter Cove, Antarctica, newly ice-free areasappeared due to glacial retreat. Simultaneously, the inflowof sediment increased, reducing underwater photosyntheticallyactive radiation (PAR, 400?700 nm). The aim ofthis study was to determine the photosynthetic characteristicsof two macroalgal species colonizing three newly icefreeareas, A1, A2 and A3, with increasing degree of glacialinfluence from A1 to A3. Turbidity, salinity and temperaturewere measured, and light attenuation coefficients(Kd) calculated and considered as a proxy for glacialsediment input. The lower depth distribution of the red algaPalmaria decipiens and the brown alga Himantothallusgrandifolius was 10 m in A3, 20 m in A2 and 30 m in A1.Both species were then collected, at 5 and 10 m at all areas.Photosynthetic parameters and the daily metabolic carbonbalance (CB) were determined. Kd was significantly higherin A3 compared with A1 and A2. The CB of P. decipienswas significantly higher in A1 followed by A2 and A3, andsignificantly higher at shallower than at greater depth. ForH. grandifolius CB was significantly lower in A3 and in A2at deeper depths compared with the rest of areas anddepths. The lower distribution limit of the algae waspositively correlated to the light penetration. An increase inthe sediment run-off due to global warming might lead toan elevation of the lower depth distribution limit but retreatingglaciers can open new space for macroalgalcolonization. These changes will probably affect macroalgalprimary productivity in Potter Cove with consequencesfor the coastal ecosystem.