This study successfully isolated and screened a microbial strain with efficient alginate-degrading capability from seaweed, utilizing alginate as the sole carbon source in a selective culture medium. The strain was systematically identified and subjected to bioinformatics analysis through physiological and biochemical characterization, 16S rDNA sequence analysis, and whole-genome sequencing to uncover potential alginate lyase-related genes. Additionally, the enzyme production conditions for the strain were optimized using single-factor experiments, Plackett-Burman design, and response surface methodology. Morphological observations, physiological and biochemical trait analysis, and 16S rDNA gene sequence identification confirmed the strain to be of the genus Cobetia. The full length of the strain’s genome is 4136490 base pairs, with a GC content of 62.48%. Genome prediction encoded 3454 protein-coding genes, 70 tRNA genes, and 12 rRNA genes. Nucleotide consistency analysis was subsequently performed and it was named Cobetia marina 29. Nucleotide consistency analysis was subsequently performed and it was named Cobetia marina 29. Functional annotation using the GO, KEGG, COG, and CAZy databases yielded 2487, 2271, 2910, and 145 annotated functional genes, respectively. Among these, three genes encoded alginate lyases and were classified into the PL17 and PL7 families. Finally, the cultivation parameters were refined, and under the optimal conditions for enzyme production, the enzyme activity was enhanced to 179.29 U/mL, which represented a 53.6% increase compared with the levels prior to optimization. The findings of this study provided a new microbial resource for the biodegradation of alginate and laid the foundation for subsequent industrial applications.