A remarkable lack of punctual and comparable data on the availability of trophic resources characterizes most studies relating biodiversity and food webs, but decapod crustaceans will help, in this study, finding some peculiar common trends of ecosystems. Structural properties of networks, as statistically investigated, affect their stability and food webs are ultimately considered as complex networks of biotic interactions. Fixed mathematical limits constrain the number of species naturally assembled in a community, even if species composition was progressively modified by climate changes: the biodiversity has space constraints. Consequently, since there is less space at higher latitudes than at lower ones, less species may be predicted to globally co-exist, as the planet warms up and the oceans acidify. Here, according to some key mathematical relationships of networks, we forecast an inverse relationship between connectance (a specific feature of food webs) and species diversity. In this chapter, we will apply these relationships to test a general model of biodiversity trends based on the responses of crustacean decapods to the abundance of feeding sources, in a range of environments variably impacted by O.A. The conclusions reached within this chapter will demonstrate consistent properties characterizing the assemblages of aquatic creatures, and extensible to various structural levels, from single cells to the largest ecosystems