A model for the biomass–density dynamics of seagrasses developed and calibrated on global data

Abstract

BackgroundSeagrasses are foundation species in estuarine and lagoon systems, providing a wide array of services for the ecosystem and the human population. Understanding the dynamics of their stands is essential in order to better assess natural and anthropogenic impacts. It is usually considered that healthy seagrasses aim to maximize their stand biomass (g DW m−2) which may be constrained by resource availability i.e., the local environment sets a carrying capacity. Recently, this paradigm has been tested and reassessed, and it is believed that seagrasses actually maximize their efficiency of space occupation—i.e., aim to reach an interspecific boundary line (IBL)—as quick as possible. This requires that they simultaneously grow in biomass and iterate new shoots to increase density. However, this strategy depresses their biomass potential.Resultsto comply with this new paradigm, we developed a seagrass growth model that updates the carrying capacities for biomass and shoot density from the seagrass IBL at each time step. The use of a joint biomass and density growth rates enabled parameter estimation with twice the sample sizes and made the model less sensitive to episodic error in either of the variables. The use of instantaneous growth rates enabled the model to be calibrated with data sampled at widely different time intervals. We used data from 24 studies of six seagrass species scattered worldwide. The forecasted allometric biomass–density growth trajectories fit these observations well. Maximum growth and decay rates were found consistently for each species. The growth rates varied seasonally, matching previous observations.ConclusionsState-of-art models predicting both biomass and shoot density in seagrass have not previously incorporated our observation across many seagrass species that dynamics depend on current state relative to IBL. Our model better simulates the biomass–density dynamics of seagrass stands while shedding light on its intricacies. However, it is only valid for established patches where dynamics involve space-filling, not for colonization of new areas.Electronic supplementary materialThe online version of this article (10.1186/s12898-019-0221-4) contains supplementary material, which is available to authorized users.

Ecological and Behavioral Drivers of Supplemental Feeding Use by Roe Deer Capreolus capreolus in a Peri-Urban Context

“…For each sex, we plotted rose diagrams, which display the 24 h diel cycle and the frequency of use of each hour, and extracted the circular mean of distributions. In order to assess whether the distributions deviated from uniform, we ran the non-parametric Hermans–Rasson test, which is recommended when circular data follow multimodal distributions [ 36 ]. We then performed a pairwise test to compare the male and female distributions.…”

Population structure of a newly recorded (Halodule uninervis) and native seagrass (Halophila ovalis) species from an intertidal creek ecosystem

“…Density and biomass are essential indicators of seagrass health and ecosystem status (Ali et al, 2018;Vieira et al, 2019). Though there are 71 and 51 publications from the coast of India for H. ovalis and H. uninervis, respectively, that focus on the Indian coast , there is a significant lack of density and biomass values of both seagrasses.…”

“…environmental variables on seagrass (Priyadarsini et al, 2014;Sahu et al, 2014). However, these studies lack proper density, biomass and morphometric values of the various seagrass species, which are essential indicators of seagrass health (Ali et al, 2018;Vieira et al, 2019). Consequently, the only morphometric studies on H. ovalis are from the Haripur creek area, located 32-km away from the southeast part of the Chilika lagoon (Figure 3), where H. ovalis was first reported being away from the Chilika lagoon (Mahapatro et al, 2014).…”

Seagrasses benefit from mild anthropogenic nutrient additions

“…Alongside this, an interspecific boundary line (IBL) was determined as the upper limit for any plant stand on Earth, thus setting the maximum for efficient packing of biomass in space in plant stands (Weller, 1989;Scrosati, 2000). Recently, revised IBLs have been determined for algae (Creed et al, 2019) and for seagrasses (Vieira et al, 2018(Vieira et al, , 2019. Both the self-thinning theory and IBL determination rely on the stand biomass (B) vs. density (D) plotted on log scales, i.e., log 10 B=a+b×log 10 D. In the case of seagrasses, "density" refers to shoots•m -2 and its original IBL had constants a = 4.569 and b = -0.438 (Vieira et al, 2018).…”