## 4 Conclusions  
This is the first study assessing the ecotoxicological effects of SiNC-DCOIT, a novel AF nanomaterial, in a tropical marine species. The present findings reinforce the importance of balancing toxicity towards non-target species and efficacy against fouler species when developing a novel AF biocide. Using the mussel _P. perna_, as a model to holistically assess DCOIT in a dissolved and nanostructured forms, it was possible (a) to confirm that DCOIT is very efficient inhibiting the attachment of juvenile _P. perna_, nevertheless extremely toxic towards gametes and very early stages of the tested mussels; (b) to demonstrate that SiNC-DCOIT can be even more efficient than DCOIT, by preventing the formation of the _P. perna_ veliger larvae, which can be the critical to control the undesired settlement of such fouler species on coated immersed surfaces; (c) to corroborate the lower toxicity of SiNC-DCOIT (comparing with DCOIT), now on fertilized gametes and juveniles of _P. perna_, thus ensuring the ecological success of the natural populations of this species.  
Therefore, SiNC-DCOIT can be regarded as promising AF additive for maritime coatings that poses lower environmental risk while can successfully tackle the adhesion of larvae of _P. perna_ thanks to the controlled biocidal release of this engineered nanomaterial. Future integrative studies would unveil the holistic effects on tropical marine biota and environment.  
Conceptualization, R.M. and F.C.P.; validation, R.M., D.M.d.S.A. and F.C.P.; formal analysis, J.V.N.d.S. and F.C.P.; investigation, J.V.N.d.S., R.M., M.K.F., B.G.d.C., M.B.M.d.Pe.S. and F.C.P.; resources, R.M. and F.M.; writing--original draft preparation, J.V.N.d.S. and F.C.P.; writing--review and editing, J.V.N.d.S., R.M., M.K.F., B.G.d.C., M.B.M.d.Pe.S., D.M.d.S.A. and F.C.P.; supervision, R.M. and F.C.P.; project administration, R.M. and D.M.d.S.A.; funding acquisition, R.M. and D.M.d.S.A. All authors have read and agreed to the published version of the manuscript.  
This project was carried out in the framework of the bilateral project \"Exposure and bioaccumulation assessment of anti-fouling nanomaterials in marine organisms from temperate and tropical waters\" funded by Fundacao para a Ciencia e a Tecnologia--FCT (ref. 4265 DRI/FCT), Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--CAPES (Process #88881.156405/2017-01) and the project NANOGREEN (CIRCNA/BRB/0291/2019) funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19 (CEECIND/01329/2017). JVNS (grant CNPq #46593), MBMPS (grant CNPq #53805) and DMSA (grants #31609/2014-7 and #308533/2018-6) is funded by National Council for Scientific and Technological Development--CNPq. MKGF (grant FAPESP #2016/24033-3), BGC (grants FAPESP #2017/10211-0 and #2019/19898-3) and MBMPS (grant FAPESP #2018/25379-6) is funded by Sao Paulo Research Foundation--FAPESP. FCP is funded by CAPES (grant CAPES #8887.12410/2016-00). Thanks are also due to the financial support to CESAM (UIDP/50017/2020 + UIDB/50017/2020), through national funds.  
**Acknowledgments:** We acknowledge Smallmatek by providing all test materials.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.