Patch dynamics of the Mediterranean seagrass Posidonia oceanica: Implications for recolonisation process |
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| Institution: | 1. Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas, Blanes, Spain;2. EcoPast (GI-1553), Facultade de Bioloxia, Universidade de Santiago de Compostela, Santiago de Compostela, Spain;3. Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Barcelona, Spain;4. Departament de Física, Universitat Autònoma de Barcelona, Barcelona, Spain;5. School of Natural Sciences, Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Australia;1. Andromède Océanologie, 7 Place Cassan, 34280 Carnon, France;2. UMR 5554 – ISEM, Campus triolet de l''Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France;3. Agence de l''eau Rhône-Méditerranée-Corse, Immeuble le Noailles, 62 La Canebière, 13001 Marseille, France;1. Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, 80121 Naples, Italy;2. Department of Life Sciences, University of Trieste, 34127 Trieste, Italy;3. CNR-IAS, Lungomare Cristoforo Colombo 4521, 90149 Palermo, Italy;4. Seagrass Ecology Group, Oceanographic Center of Murcia, Spanish Institute of Oceanography, Murcia, Spain;5. CNR-IAS, Via del Mare 3, 91021 Torretta Granitola, Italy |
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| Abstract: | Patch dynamics of the Mediterranean slow-growing seagrass Posidonia oceanica was studied in two shallow sites (3–10 m) of the Balearic Archipelago (Spain) through repeated censuses (1–2 year?1). In the sheltered site of Es Port Bay (Cabrera Island), initial patch density (October 2001) was low: 0.05 patches m?2, and the patch size (number of shoots) distribution was bimodal: most of the patches had less than 6 shoots or between 20 and 50 shoots. Mean patch recruitment in Es Port Bay (0.006 ± 0.002 patches m?2 year?1) exceeded mean patch loss (0.001 ± 0.001 patches m?2 year?1), yielding positive net patch recruitment (0.004 ± 0.003 patches m?2 year?1) and a slightly increased patch density 3 years later (July 2004, 0.06 patches m?2). In the exposed site of S’Estanyol, the initial patch density was higher (1.38 patches m?2, August 2003), and patch size frequency decreased exponentially with size. Patch recruitment (0.26 patches m?2 year?1) and loss (0.24 patches m?2 year?1) were high, yielding a slightly increased patch density in the area 1 year later (October 2004, 1.40 patches m?2). Most recruited patches consisted of rooting vegetative fragments of 1–2 shoots. Seedling recruitment was observed in Summer 2004 at both sites. Episodic, seedling recruitment comprised 30% and 25% of total patch recruitment in Es Port Bay and S’Estanyol, respectively. Patch survival increased with patch size and no direct removal was observed among patches of 5 shoots or more. Most patches grew along the study, shifting patch distribution towards larger sizes. Within the size range studied (1–150 shoots), absolute shoot recruitment (shoots year?1) increased linearly with patch size (R2 = 0.64, p < 4 × 10?5, N = 125), while specific shoot recruitment was constant (about 0.25 ± 0.05 year?1), although its variance was large for small patches. Given the slow growth rate and the high survival of patches with 5 or more shoots, even the low patch recruitment rates reported here could play a significant role in the colonisation process of P. oceanica. |
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