Seed nutrient content and nutritional status of Posidonia oceanica seedlings in the northwestern Mediterranean Sea

Abstract

We studied nutritional constraints on growth of Posidonia oceanica seedlings, morphometry and elemental content of mature seeds, and seedlings stranded on a beach of the northwestern Mediterranean Sea on 3 dates (May 2004, May 2005 and December 2005. The mean total nitrogen (N) and phosphorus (P) content of P. oceanica seeds was high compared with closely related species. Seeds varied considerably in mass, and their nutrient and carbon (C) content increased linearly with mass. This indicates substantial variation in the amount of reserves initially available for seedling growth. Stored reserves in seeds were used by seedlings within 6 to 8 mo after germination: P was retrieved with greater efficiency (86%) than was N (69%) and C (20%). From May to December of the 2nd year (2005), the tissue nutrient concentrations of seedlings declined due to fast utilization and translocation of nutrients from the internal pools to support summer growth. Instead the C concentration in roots and rhizomes increased, indicating an accumulation of C. Seedling tissue N and P concentrations were above the critical levels reported for seagrasses, and were also lower than those of plagiotropic rhizomes of P. oceanica collected in the same period. These results suggest that P may play a major role in constraining growth of P. oceanica seedlings. KEY WORDS: Seeds · Seedlings · Nutritional constraints · Morphometric analysis · Elemental analysisResale or republication not permitted without written consent of the publisher

Seagrass (Posidonia oceanica) seedlings in a high-CO2 world: from physiology to herbivory

“…This effect of increased non-structural carbohydrates in belowground tissues has been also found in adult seagrasses under experimental increase in CO 2 availability3239. In seedlings, this is particularly important since seeds store and supply carbon and nutrients to the seedling during the first year of its life57. Increased carbon reserves and biomass of the seed would benefit seedling survival and resilience to stressful conditions, especially in seagrasses such as P. oceanica in which the buoyant fruits disperse to new habitats away from the original meadow.…”

Seed photosynthesis enhances Posidonia oceanica seedling growth

“…Therefore, the generally low N:P ratio in both light and dark treatments in comparison with the atomic ratio observed in a field study using older seedlings with deflated reserves (Balestri et al 2009) corroborates that, during early seedling development, P is not a limiting factor due to the high seed reserves. The lower N:P of PL and FD could indicate stress on seedling growth due to lack of photosynthesis rather than a nutrient limitation.…”

“…Flowering and fruit production is highly variable in space and in time, with intensive synchronised flowering episodes occurring at 8-to 10-year intervals (Balestri et al 2003, Diaz-Almela et al 2006. The green seed remains attached to the young plant for one to two years after germination and supplies C, N and P to the developing seedling until about one year after germination (Balestri et al 2009). The buoyant fruits are transported by currents away from parental shoots, enabling dehisced seeds to colonize sites outside the range of vegetative growth (Buia and Mazzella 1991).…”

Use of Posidonia oceanica seedlings from beach-cast fruits for seagrass planting

“…The culture of beach-cast seeds of P. oceanica in aquaria to produce seedlings is a straightforward procedure that has been repeatedly demonstrated (Caye and Meinesz 1989, Buia and Mazzella 1991, Meinesz et al 1993, Bedini 1997, Balestri et al 1998, Belzunce et al 2008. Carbon and nutrient reserves contained in the seed are thought to be sufficient to allow the vegetative development of seedlings for 6 -8 months after germination (Belzunce et al 2008, Balestri et al 2009 ).…”