Herbivory is a key structuring force that can have negative, positive, or mixed impacts on seagrasses. The identity and abundance of herbivores, as well environmental conditions such as solar insulation, can influence the impacts of herbivory. To understand the impact of herbivores on turtlegrass in warm, temperate St. Joseph Bay (SJB) in the northeastern Gulf of Mexico, we estimated densities of the most common herbivores: variegated sea urchins and green turtles. We also estimated SJB’s herbivore carrying capacities by estimating annual average turtlegrass production and variegated urchin consumption rates and by using previously calculated juvenile green turtle consumption rates and seagrass area. During summer, turtlegrass exhibited compensatory growth due to urchin herbivory, but during winter, turtlegrass growth was negatively affected by urchin grazing. Given our calculated annual turtlegrass production, urchin ingestion rates, and the average urchin density of 5.89 ± 0.09 (SE) urchins ha⁻¹, the turtlegrass production not consumed by urchins can sustain 278.0 juveniles ha⁻¹, or about 556,010 turtles, putting current average green turtle abundance of 26 ± 3.7 individuals ha⁻¹ at 4.0–14.6% of carrying capacity. Previous work in this system has shown that simulated turtle herbivory can reduce turtlegrass productivity—with this potential reduction in production, SJB could not sustain a green turtle population at current urchin densities. Given the rapid global green turtle increase, evaluating densities and future carrying capacities of herbivores in higher latitude seagrass pastures is critical for updating and achieving recovery goals for both green turtles and globally declining seagrass meadows.

草食是一种关键的结构力量，会对海草产生负面，正面或不同的影响。食草动物的身份和丰富性以及诸如太阳能隔热等环境条件会影响食草动物的影响。为了了解草食动物对墨西哥湾东北部温带温带圣约瑟夫湾（SJB）turtle草的影响，我们估算了最常见的草食动物的密度：杂色海胆和绿海龟。我们还通过估算年平均turtle草产量和各种海胆消耗率，以及使用先前计算的少年绿turtle消耗率和海草面积来估算SJB的草食动物承载能力。在夏季，turtle草由于野孩子食性而表现出补偿性生长，但在冬季，海草放牧对龟草的生长有不利影响。考虑到我们计算出的每年turtle草产量，海胆摄入率以及平均海胆密度为5.89±0.09（SE）的海胆ha^-1，未由海胆消耗的gra草产量可维持278.0少年ha ^-1，或约556,010只龟，使目前平均绿green丰度为26±3.7个体ha ^-1，承载能力为4.0–14.6％。该系统以前的工作表明，模拟的龟食性动物会降低龟草的生产力，由于这种潜在的产量下降，SJB无法在目前的海胆密度下维持绿龟种群。鉴于全球绿海龟的迅速增加，评估高纬度海草牧场中草食动物的密度和将来的承载能力对于更新和实现绿海龟和全球衰退的海草草甸的恢复目标至关重要。