Merfolk Commander

I'm missing at least one important card for commander, Empress Galina while I see you already have Thada Adel, Aquisitor added. Both have there values while Galina can steal nearly anything legendary (since the rules changed even Planswalkers and your opponents commander) while Thada has two advantages; she first has Islandwalk on her own and second will grab any artifact from your opponents deck so "second Sol Ring anyone?".

You could also consider to add Kira, Great Glass-Spinner as an addition to Kopala. It may not be a Merfolk but also has its values.
A second good non-Merfolk supporter card I like to play is Patron Wizard. Since most Merfolk you play are Wizards too, they can be utilized to counter spells just for tapping them with Patron Wizard. Fallowsage for example profits from this while helping to counter it will also draw a card.

What happened to good old True-Name Nemesis?

A board finisher could also be Deepchannel Mentor because it makes any of your blue cards unblockable, he may get the final strike.

So now to some cards of your deck: Augur of Bolas seems a little misplaced here because you run just 11 spells it could target, what are 11% of your deck while it will in 89% of the cases throw away some cards that might have been important for you. If you like to run a filter creature, consider for another Forerunner of the Heralds card, Tidal Courier. Merfolk Wayfinder is the same for Island cards targeting any Island card just like Breeding Pool too.

For a bit more power you could also add Metallic Mimic as a second Deeproot Elite and while your commander is Kumena, also Sage of Fables. Sage also adds counters your your Wizards cards and can utilize those for drawing a card for each counter on target creature. Shapers of Nature's second ability costs one blue mana more but is also an alternative