Inter-annual variation of shoot density and biomass, nitrogen and phosphorus content of the leaves, and epiphyte load of the seagrass <i>Posidonia oceanica</i> (L.) Delile off Mallorca, western Mediterranean

Abstract

SUMMARY:The epiphyte load, the ash content of the epiphytes, the leaf biomass, the nitrogen and phosphorus content of the leaves, and the density of shoots of the Mediterranean seagrass Posidonia oceanica (L.) Delile were monitored yearly from 2003 to 2008 in two shallow meadows off Mallorca (western Mediterranean) with the aim of identifying the responses of P. oceanica meadows to mid-term environmental variability. Inter-annual variability of P. oceanica meadows was significant for most of the descriptors examined: shoot biomass, epiphyte load, nitrogen and phosphorus content of the leaves, and shoot density. Shoot density increased by a factor of 2 and epiphyte load by a factor of 4 from 2003 to 2008. P. oceanica descriptors were generally not correlated with each other or with the average sea surface temperature during August. Long-term data series of descriptors of P. oceanica status are essential to improve understanding about the response of this important Mediterranean coastal ecosystem to natural and anthropogenic disturbances and to assess the effects of rapid global environmental change.Keywords: inter-annual variation, seagrass, epiphyte load, nitrogen, phosphorus, Posidonia oceanica, Western Mediterranean. RESUMEN: Variación interanual de la densidad de haces, biomasa foliar del haz, concentración de nitróge-no y fósforo en las hojas y de la carga de epífitos de la angiosperma marina Posidonia oceanica (L.) Delile en Mallorca, Mediterráneo occidental. -La carga de epífitos, el contenido en cenizas de los mismos, la biomasa foliar, el contenido en nitrógeno y fósforo de las hojas y la densidad de haces de la angiosperma marina Posidonia oceanica (L.) Delile se midieron anualmente desde 2003 a 2008 en dos praderas someras en Mallorca (Mediterráneo occidental) para identificar la respuesta de las praderas de P. oceanica a la variabilidad ambiental a medio plazo. Las praderas de P. oceanica presentan una gran variabilidad interanual pues la mayoría de los descriptores examinados (densidad de haces, biomasa foliar del haz, concentración de nitrógeno y fósforo en las hojas y carga de epífitos) cambiaron durante el periodo [2003][2004][2005][2006][2007][2008]. La densidad de haces se multiplicó por dos mientras que la carga de epífitos lo hizo por cuatro. No se encontró correlación entre la mayoría de los descriptores de P. oceanica ni tampoco con la temperatura del agua superficial del mar en agosto. La obtención de series temporales a largo plazo sobre descriptores del estado de las praderas de P. oceanica es necesaria para mejorar la comprensión de las respuestas de este importante ecosistema costero del Mediterráneo a perturbaciones naturales y antropogénicas y para evaluar los efectos del cambio global.Palabras clave: variación interanual, angiospermas marinas, epífitos, nitrógeno, fósforo, Posidonia oceanica, Mediterráneo occidental.

Vertical Configuration of a Side Scan Sonar for the Monitoring of Posidonia oceanica Meadows

“…This result may be contrary to what was expected, since previous studies have shown how the energy of the echo at high frequencies tends to increase with the increasing seagrass biomass [45]. Nevertheless, biomass and shoot density do not necessarily present a positive relationship [50,51], since the number of leaves per shoot varies as well as the leaf length, owing to several factors, such as the season or the occurrence of severe storms. In addition, there are other factors that can contribute to decreasing the level of the echo when the density increases.…”

Epiphyte assemblages of the Mediterranean seagrassPosidonia oceanica: an overview

“…). Owing to inter‐annual variations in epiphyte loads (Terrados & Medina Pons ), sampling designs with a number of controls suitable to separate the natural and human‐induced variability of the system are needed (De Biasi et al . ).…”

“…In shallow meadows, the loss of old P. oceanica leaves occurs in late summer, whereas this occurs later in deep meadows, where it is possible to observe highly colonized old leaves in autumn (Mazzella & Ott ). Inter‐annual variations in epiphyte load have also been observed (Terrados & Medina Pons ). Changes in epiphyte abundance may be related to changes in herbivore pressure or nutrient availability.…”

The biomass–density relationship in seagrasses and its use as an ecological indicator

“…obs. Location Latitude Cymodocea nodosa Agostini et al [ 72 ] 12 Urbinu lagoon, Corsica 42.02 Cymodocea nodosa Duarte and Sand-Jensen [ 71 ] 47 Ebro Delta, Spain 40.72 Cymodocea nodosa Sghaier et al [ 75 ] 36 Monastir Bay, Tunisia 35.37 Cymodocea nodosa Peduzzi and Vukovic [ 74 ] 17 Golf of Trieste, Italy 45.7 Cymodocea nodosa Cunha e Duarte [ 73 ] 5 Ria Formosa, Portugal 37.10 Halodule wrightii Hall et al [ 60 ] 12 Florida Bay, USA 25.14 Halodule wrightii Creed (this study) 992 Multiple sites, American continent – Posidonia oceanica Terrados and Pons [ 76 ] 5 Magaluf, Mallorca Island, Spain 39.30 Posidonia oceanica Terrados and Pons [ 76 ] 5 Ses Salines, Mallorca Island, Spain 39.15 Posidonia sinuosa Keulen [ 77 ...…”