Consumers often deplete local resources and aggregate along edges of remaining resources, forming “consumer fronts.” We examined the factors that promote Sesarma reticulatum crab aggregations at saltmarsh creek heads to explain the directional but slow movement of these fronts. We also created artificial creek heads to test the hypothesis that hydrological conditions at creek heads create superior habitat for crabs. Soil temperatures were ˜11–12% cooler, hydrogen sulfide concentrations lower (0.0 vs. ˜0.58 mg/L), and dissolved oxygen concentrations twofold higher at the creek head versus the marsh platform. In the artificial creek-head experiment, altering hydrological conditions led to lower dissolved sulfide levels, higher dissolved oxygen levels, and increased densities of crab burrows and Sesarma crabs. Moreover, the elevation of the soil surface declined rapidly at artificial creek heads versus controls, suggesting that crabs were increasing erosion. Our results suggest that abiotic conditions for crabs are better at the leading edge of the creek head than the trailing edge, explaining the directional movement of the front. Moreover, the speed at which the front propagates appears to be limited by the rate at which the creekhead erodes, rather than by crab mobility. The directional and slow movement of Sesarma fronts compared to consumer fronts of other invertebrates appears to result from the inextricable link between Sesarma and marsh geomorphology, whereas other consumer fronts are associated mostly with food resources.

中文翻译：

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与盐沼中的小溪头相关的消费者前沿的定向运动

消费者经常耗尽当地资源并沿着剩余资源的边缘聚集，形成“消费者阵线”。我们研究了促进Sesarma reticulatum蟹在盐沼溪头聚集的因素，以解释这些前沿的定向但缓慢的运动。我们还创建了人工河头来测试河头的水文条件为螃蟹创造优越栖息地的假设。土壤温度降低约 11-12%，硫化氢浓度降低（0.0 对约 0.58 毫克/升），河头处的溶解氧浓度比沼泽平台高两倍。在人工河口实验中，改变水文条件导致溶解硫化物含量降低、溶解氧含量升高、蟹洞和螃蟹的密度增加。芝麻蟹。此外，与对照相比，人工河头处的土壤表面高度迅速下降，这表明螃蟹正在加剧侵蚀。我们的结果表明，螃蟹的非生物条件在溪头的前缘比后缘更好，这解释了前缘的定向运动。此外，锋面传播的速度似乎受到溪头侵蚀速度的限制，而不是受到螃蟹移动的限制。与其他无脊椎动物的消费前沿相比，Sesarma前沿的定向和缓慢移动似乎是由Sesarma和沼泽地貌之间不可分割的联系造成的，而其他消费前沿主要与食物资源相关。