# Laminar _Ulva_ Species: A Multi-Tool for Humankind?
## 2 The Biology of _Ulva_ sp.
### Mutualistic Symbiotic Relationships  
Another example was the case of the investigation in Veerse Meer, a brackish lagoon located in the southwest of the Netherlands carried out by [PERSON] et al., 2002 [69] on the role of isopod and amphiped grazing in _Ulva_ spp. They identified the amphiped _Gammarus locusta_ and the isopods _Idotea chelipes_ and _Sphaeroma hookeri_ as potential herbivores of _Ulva_ spp. However, in the presence of epiphytic diatoms on _Ulva_ spp. thalli, _Gammarus_ and _Sphaeroma_ species primarily grazed on the diatoms rather than on the _Ulva_tissue. Only _Iotaea_ continued to graze on _Ulva_ spp. In a laboratory experiment, it was found that _Gammaus_ had a positive effect on _Ulva_ growth, likely due to its selective removal of epiphytic diatoms from the thalli. Herbivores that remove epiphytes, such as _Gammaus_, may stimulate _Ulva_ development, thereby explaining the higher growth rates observed in the field. When assessing the potential role of herbivorous invertebrates in reducing macroalgal biomass accumulation, it is crucial to consider epiphyture abundance on macroalgae. Preferential removal of epiphytes may promote growth and consequently have an opposite effect [4,69]. [PERSON] et al., 2018 [67], when working on a proposed framework for the integrated management of marine pests in seaweed cultivation, based on several cases studied, noted that a low density of _Ulva rigida_ and _Cladophora_ sp. (minimum 11.5 g) under closed in-door plastic photobioreactor culture led to culture collapse due to proliferation of epiphytes (other marine algae, nematodes, copepods, and bacteria), but a high inoculum density (minimum 179-264 g) yielded a 15% daily growth rate. Furthermore, the culture of _Ulva_ sp. in a cage with the inclusion of a double safety net resulted in a daily growth rate of 8.1% per day in open sea agriculture in Israel in a one-month growth cycle, which in the absence of the safety net dropped to \(-2.5\%\) per day [67]. Finally, it should be noted that the composition of the microbiome associated with _Ulva_ sp. changes depending on geographic location, seasonality, and abiotic factors such as temperature, salinity, depth, light, etc. Therefore, understanding this microbiome-_Ulva_ complex is essential given its importance for the adaptation of _Ulva_ spp. to their environment, which will vary between aquaculture systems [70]. Metabolomic Profile  
Metabolites are compounds, generally organic, that participate in chemical reactions that occur at the cellular level. Classified as primary and secondary, they are differentiated by whether they are directly involved or not in the normal growth, development, and reproduction of an organism. Some authors like [71,72] consider that metabolites released into the environment \"act as spoken language, transmitting signals from the genetic architecture and the environment.\" Therefore, metabolomics can help provide a functional understanding of an organism's physiological state or symbiotic interactions [73]. A study was carried out to investigate the metabolic profiles of _U. prolifera_ during proliferation induced by fragmentation. Filaments and fragments were collected at intervals of 12, 24, 36, 48, 60, 72, 96, and 120 h and subjected to metabolic profile analysis using GC-MS. Within 48 h, the procedure detected a dynamic shift in the metabolic profile. A total of 156 metabolites were measured, with 63 showing substantial change. GABA, glutamic acid, gallic acid, and malic acid are the metabolites responsible for the creation and release of reproductive cells. Furthermore, n-hexanol, 2-methyl-3-phenylindole, and 3-indoleacetonitrile were responsible for stress reduction. Changes in the levels of metabolites including sugars, organic acids, and alcohol with photoperiod may be the strategy adopted by _U. prolifera_ to deal with fragmentation in nature [74]. According to [PERSON] et al.